U.S. patent application number 10/119126 was filed with the patent office on 2002-12-05 for radiation-curable optical glass fiber coating compositions, coated optical glass fibers, and optical glass fiber assemblies.
This patent application is currently assigned to DSM N.V.. Invention is credited to Bishop, Timothy E., Chawla, Chander P., Lapin, Stephen C., Pasternack, George, Petisce, James R., Snowwhite, Paul E., Szum, David M., Vandeberg, John T., Zahora, Edward P..
Application Number | 20020181913 10/119126 |
Document ID | / |
Family ID | 27419330 |
Filed Date | 2002-12-05 |
United States Patent
Application |
20020181913 |
Kind Code |
A1 |
Szum, David M. ; et
al. |
December 5, 2002 |
Radiation-curable optical glass fiber coating compositions, coated
optical glass fibers, and optical glass fiber assemblies
Abstract
Optical fiber coatings are disclosed having excellent ribbon
stripping and adhesion behavior. The coatings are
radiation-curable. The excellent stripping and adhesion behavior
can be achieved by several means which include by use of additives,
by use of radiation-curable oligomers having higher molecular
weight, or by use of coatings having certain thermal properties.
Combination of means can be employed. Stripping behavior can be
measured by crack propagation and fiber friction measurements.
Inventors: |
Szum, David M.; (Elmhurst,
IL) ; Chawla, Chander P.; (Batavia, IL) ;
Petisce, James R.; (West Dundee, IL) ; Vandeberg,
John T.; (Barrington, IL) ; Pasternack, George;
(Riverwoods, IL) ; Bishop, Timothy E.; (Algonquin,
IL) ; Snowwhite, Paul E.; (Elgin, IL) ;
Zahora, Edward P.; (Naperville, IL) ; Lapin, Stephen
C.; (Waterford, WI) |
Correspondence
Address: |
Pillsbury Winthrop LLP
Intellectual Property Group
1600 Tysons Boulevard
McLean
VA
22102
US
|
Assignee: |
DSM N.V.
|
Family ID: |
27419330 |
Appl. No.: |
10/119126 |
Filed: |
April 10, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10119126 |
Apr 10, 2002 |
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10004410 |
Dec 6, 2001 |
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10004410 |
Dec 6, 2001 |
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09838140 |
Apr 20, 2001 |
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6339666 |
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09838140 |
Apr 20, 2001 |
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09035771 |
Mar 6, 1998 |
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6298189 |
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09035771 |
Mar 6, 1998 |
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08877585 |
Jun 17, 1997 |
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08877585 |
Jun 17, 1997 |
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08840893 |
Apr 17, 1997 |
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08840893 |
Apr 17, 1997 |
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08745790 |
Nov 8, 1996 |
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Current U.S.
Class: |
385/128 ;
522/1 |
Current CPC
Class: |
C03C 25/1065
20130101 |
Class at
Publication: |
385/128 ;
522/1 |
International
Class: |
G02B 006/22; C08F
002/46 |
Claims
What is claimed is:
1. A radiation-curable inner primary coating composition for an
optical glass fiber comprising an oligomer having at least one
functional group capable of polymerizing under the influence of
radiation, said composition after radiation cure having the
combination of properties of: (a) a fiber pull-out friction of less
than 20 g/mm at stripping temperature; (b) a crack propagation of
greater than 1.0 mm at stripping temperature; (c) a glass
transition temperature of below 10.degree. C.; and (d) sufficient
adhesion to said glass fiber to prevent delamination in the
presence of moisture and during handling.
2. A system for coating an optical glass fiber comprising a
radiation-curable inner primary coating composition and a
radiation-curable outer primary coating composition wherein: said
inner primary coating composition comprises an oligomer having at
least one functional group capable of polymerizing under the
influence of radiation, said inner primary coating composition
after radiation cure having the combination of properties of: (a) a
fiber pull-out friction of less than 40 g/mm at stripping
temperature; (b) a crack propagation of greater than 1.0 mm at
stripping temperature; (c) a glass transition temperature of below
10.degree. C.; and (d) sufficient adhesion to said glass fiber to
prevent delamination in the presence of moisture and during
handling; and said outer primary coating composition comprises an
oligomer having at least one functional group capable of
polymerizing under the influence of radiation, said outer primary
coating composition after radiation cure having the combination of
properties of: (e) a glass transition temperature of above
40.degree. C.; and (f) a modulus of elasticity of between about 10
MPa to about 40 MPa at stripping temperature; and wherein the ratio
of the change in length of said inner primary coating composition,
after radiation cure, to the change in length of said outer primary
coating composition, after radiation cure, is less than 2 when said
cured compositions are heated from 25.degree. C. to stripping
temperature.
3. A coated optical glass fiber, coated with at least an inner
primary coating and an outer primary coating, wherein said inner
primary coating is comprised of a radiation cured polymeric
material having the combination of properties of: (a) a fiber
pull-out friction of less than 40 g/mm at stripping temperature;
(b) a crack propagation of greater than 1.0 mm at stripping
temperature; (c) a glass transition temperature of below 10.degree.
C.; and (d) sufficient adhesion to said glass fiber to prevent
delamination in the presence of moisture and during handling; and
said outer primary coating is comprised of a radiation cured
polymeric material having the combination of properties of: (e) a
glass transition temperature of above 40.degree. C.; and (f) a
modulus of elasticity of between about 10 MPa to about 40 MPa at
stripping temperature; and wherein the ratio of the change in
length of said inner primary coating composition, after radiation
cure, to the change in length of said outer primary coating
composition, after radiation cure, is less than 2 when said cured
compositions are heated from 25.degree. C. to stripping
temperature.
4. A ribbon assembly comprising: a plurality of coated optical
glass fibers, at least one optical glass fiber coated with at least
an inner primary coating and an outer primary coating, and
optionally an ink coating; and a matrix material bonding said
plurality of coated optical glass fibers together, wherein: said
inner primary coating is comprised of a radiation cured polymeric
material having the combination of properties of: (a) a fiber
pull-out friction of less than 40 g/mm at stripping temperature;
(b) a crack propagation of greater than 1.0 mm at stripping
temperature; (c) a glass transition temperature of below 10.degree.
C.; and (d) sufficient adhesion to said glass fiber to prevent
delamination in the presence of moisture and during handling; and
said outer primary coating is comprised of a radiation cured
polymeric material having the combination of properties of: (e) a
glass transition temperature of above 40.degree. C.; and (f) a
modulus of elasticity of between about 10 MPa to about 40 MPa at
stripping temperature; and wherein the ratio of the change in
length of said inner primary coating composition, after radiation
cure, to the change in length of said outer primary coating
composition, after radiation cure, is less than 2 when said cured
compositions are heated from 25.degree. C. to stripping
temperature.
5. A radiation-curable inner primary coating composition for an
optical glass fiber comprising an oligomer having at least one
functional group capable of polymerizing under the influence of
radiation wherein said composition, after radiation cure, having
the combination of properties of: (a) a fiber pull-out friction of
less than 20 g/mm at 90.degree. C.; (b) a crack propagation of
greater than 1.0 mm at 90.degree. C.; (c) a glass transition
temperature of below 10.degree. C.; and (d) adhesion to glass of at
least 12 g/in when conditioned at 95% relative humidity.
6. A system for coating an optical glass fiber comprising a
radiation-curable inner primary coating composition and a
radiation-curable outer primary coating composition wherein: said
inner primary coating composition comprises an oligomer having at
least one functional group capable of polymerizing under the
influence of radiation, said inner primary coating composition,
after radiation cure, having the combination of properties of (a) a
fiber pull-out friction of less than 40 g/mm at 90.degree. C.; (b)
a crack propagation of greater than 1.0 mm at 90.degree. C.; (c) a
glass transition temperature of below 10.degree. C.; and (d)
adhesion to glass of at least 12 g/in when conditioned at 95%
relative humidity; and said outer primary coating composition
comprises an oligomer having at least one functional group capable
of polymerizing under the influence of radiation, said outer
primary coating composition, after radiation cure, having the
combination of properties of: (e) a glass transition temperature of
above 40.degree. C.; and (f) a modulus of elasticity of between
about 10 MPa to about 40 MPa at 100.degree. C.; and wherein the
ratio of the change in length of said inner primary coating
composition, after radiation cure, to the change in length of said
outer primary coating composition, after radiation cure, is less
than 2 when said cured compositions are heated from 25.degree. C.
to stripping temperature.
7. A coated optical glass fiber, coated with at least an inner
primary coating and an outer primary coating, wherein said inner
primary coating is comprised of a radiation cured polymeric
material having the combination of properties of: (a) a fiber
pull-out friction of less than 40 g/mm at 90.degree. C.; (b) a
crack propagation of greater than 1.0 mm at 90.degree. C.; (c) a
glass transition temperature of below 10.degree. C.; and (d)
adhesion to glass of at least 12 g/in when conditioned at 95%
relative humidity; and said outer primary coating is comprised of a
radiation cured polymeric material having the combination of
properties of: (e) a glass transition temperature of above
40.degree. C.; and (f) a modulus of elasticity of between about 10
MPa to about 40 MPa at 100.degree. C.; and wherein the ratio of the
change in length of said inner primary coating composition, after
radiation cure, to the change in length of said outer primary
coating composition, after radiation cure, is less than 2 when said
cured compositions are heated from 25.degree. C. to stripping
temperature.
8. A ribbon assembly comprising: a plurality of coated optical
glass fibers, at least one optical glass fiber coated with at least
an inner primary coating and an outer primary coating, and
optionally an ink coating; and a matrix material bonding said
plurality of coated optical glass fibers together, wherein: said
inner primary coating is comprised of a radiation cured polymeric
material having the combination of properties of: (a) a fiber
pull-out friction of less than 40 g/mm at 90.degree. C.; (b) a
crack propagation of greater than 1.0 mm at 90.degree. C.; (c) a
glass transition temperature of below 10.degree. C.; and (d)
adhesion to glass of at least 12 g/in when conditioned at 95%
relative humidity; and said outer primary coating is comprised of a
radiation cured polymeric material having the combination of
properties of: (e) a glass transition temperature of above
40.degree. C.; and (f) a modulus of elasticity of between about 10
MPa to about 40 MPa measured at 100.degree. C.; and wherein the
ratio of the change in length of said inner primary coating
composition, after radiation cure, to the change in length of said
outer primary coating composition, after radiation cure, is less
than when said cured compositions are heated from 25.degree. C. to
stripping temperature.
9. A radiation-curable inner primary coating composition for an
optical glass fiber comprising an oligomer having at least one
functional group capable of polymerizing under the influence of
radiation, said composition after radiation cure having the
combination of properties of: (a) a fiber pull-out friction of less
than 20 g/mm at stripping temperature (b) a crack propagation of
greater than 0.7 mm at stripping temperature; (c) a glass
transition temperature of below 0.degree. C.; and (d) sufficient
adhesion to said-glass fiber to prevent . delamination in the
presence of moisture and during handling.
10. A system for coating an optical glass fiber comprising a
radiation-curable inner primary coating composition and a
radiation-curable outer primary coating composition wherein: said
inner primary coating composition comprises an oligomer having at
least one functional group capable of polymerizing under the
influence of radiation, said inner primary coating composition
after radiation cure having the combination of properties of: (a) a
fiber pull-out friction of less than 40 g/mm at stripping
temperature; (b) a crack propagation of greater than 0.7 mm at
stripping temperature; (c) a glass transition temperature of below
0.degree. C.; and (d) sufficient adhesion to said glass fiber to
prevent delamination in the presence of moisture and during
handling; and said outer primary coating composition comprises an
oligomer having at least one functional group capable of
polymerizing under the influence of radiation, said outer primary
coating composition after radiation cure having the combination of
properties of: (e) a glass transition temperature of above
40.degree. C.; and (f) a modulus of elasticity of greater than 25
MPa at stripping temperature; and wherein the ratio of the change
in length of said inner primary coating composition, after
radiation cure, to the change in length of said outer primary
coating composition, after radiation cure, is less than 2 when said
cured compositions are heated from 25.degree. C. to stripping
temperature.
11. A coated optical glass fiber, coated with at least an inner
primary coating and an outer primary coating, wherein said inner
primary coating is comprised of a radiation cured polymeric
material having the combination of properties of: (a) a fiber
pull-out friction of less than 40 g/mm at stripping temperature;
(b) a crack propagation of greater than 0.7 mm at stripping
temperature; (c) a glass transition temperature of below 0.degree.
C.; and (d) sufficient adhesion to said glass fiber to prevent
delamination in the presence of moisture and during handling; and
said outer primary coating is comprised of a radiation cured
polymeric material having the combination of properties of: (e) a
glass transition temperature of above 40.degree. C.; and (f) a
modulus of elasticity of greater than 25 MPa at stripping
temperature; and wherein the ratio of the change in length of said
inner primary coating composition, after radiation cure, to the
change in length of said outer primary coating composition, after
radiation cure, is less than 2 when said cured compositions are
heated from 25.degree. C. to stripping temperature.
12. A ribbon assembly comprising: a plurality of coated optical
glass fibers, at least one optical glass fiber coated with at least
an inner primary coating and an outer primary coating, and
optionally an ink coating; and a matrix material bonding said
plurality of coated optical glass fibers together, wherein: said
inner primary coating is comprised of a radiation cured polymeric
material having the combination of properties of: (a) a fiber
pull-out friction of less than 40 g/mm at stripping temperature;
(b) a crack propagation of greater than 0.7 mm at stripping
temperature; (c) a glass transition temperature of below 0.degree.
C.; and (d) sufficient adhesion to said glass fiber to prevent
delamination in the presence of moisture and during handling; and
said outer primary coating is comprised of a radiation cured
polymeric material having the combination of properties of: (e) a
glass transition temperature of above 40.degree. C.; and (f) a
modulus of elasticity of greater than 25 MPa at stripping
temperature; and wherein the ratio of the change in length of said
inner primary coating composition, after radiation cure, to the
change in length of said outer primary coating composition, after
radiation cure, is less than 2 when said cured compositions are
heated from 25.degree. C. to stripping temperature.
13. A radiation-curable inner primary coating composition for an
optical glass fiber comprising an oligomer having at least one
functional group capable of polymerizing under the influence of
radiation wherein said composition, after radiation cure, having
the combination of properties of: (a) a fiber pull-out friction of
less than 20 g/mm at 90.degree. C.; (b) a crack propagation of
greater than 0.7 mm at 90.degree. C.; (c) a glass transition
temperature of below 0.degree. C.; and (d) adhesion to glass of at
least 5 g/in when conditioned at 95% relative humidity.
14. A system for coating an optical glass fiber comprising a
radiation-curable inner primary coating composition and a
radiation-curable outer primary coating composition wherein: said
inner primary coating composition comprises an oligomer having at
least one functional group capable of polymerizing under the
influence of radiation, said inner primary coating composition,
after radiation cure, having the combination of properties of: (a)
a fiber pull-out friction of less than 40 g/mm at 90.degree. C.;
(b) a crack propagation of greater than 0.7 mm at 90.degree. C.;
(c) a glass transition temperature of below 0.degree. C.; and (d)
adhesion to glass of at least 5 g/in when conditioned at 95%
relative humidity; and said outer primary coating composition
comprises an oligomer having at least one functional group capable
of polymerizing under the influence of radiation, said outer
primary coating composition, after radiation cure, having the
combination of properties of: (e) a glass transition temperature of
above 4.sup.0.degree. C.; and (f) a modulus of elasticity of
greater than 25 MPa at 100.degree. C.; and wherein the ratio of the
change in length of said inner primary coating composition, after
radiation cure, to the change in length of said outer primary
coating composition, after radiation cure, is less than 2 when said
cured compositions are heated from 25.degree. C. to stripping
temperature.
15. A coated optical glass fiber, coated with at least an inner
primary coating and an outer primary coating, wherein said inner
primary coating is comprised of a radiation cured polymeric
material having the combination of properties of: (a) a fiber
pull-out friction of less than 40 g/mm at (b) a crack propagation
of greater than 0.7 mm at 90.degree. C.; (c) a glass transition
temperature of below 0.degree. C.; and (d) adhesion to glass of at
least 5 g/in when. conditioned at 95% relative humidity; and said
outer primary coating is comprised of a radiation cured polymeric
material having the combination of properties of: (e) a glass
transition temperature of above 40.degree. C.; and (f) a modulus of
elasticity of greater than 25 MPa at 100.degree. C.; and wherein
the ratio of the change in length of said inner primary coating
composition, after radiation cure, to the change in length of said
outer primary coating composition, after radiation cure, is less
than 2 when said cured compositions are heated from 25.degree. C.
to stripping temperature.
16. A ribbon assembly comprising: a plurality of coated optical
glass fibers, at least one optical glass fiber coated with at least
an inner primary coating and an outer primary coating, and
optionally an ink coating; and a matrix material bonding said
plurality of coated optical glass fibers together, wherein: said
inner primary coating is comprised of a radiation cured polymeric
material having the combination of properties of: (a) a fiber
pull-out friction of less than 40 g/mm at 90.degree. C.; (b) a
crack propagation of greater than 0.7 mm at 90.degree. C.; (c) a
glass transition temperature of below 0.degree. C.; and (d)
adhesion to glass of at least 5 g/in when conditioned at 95%
relative humidity; and said outer primary coating is comprised of a
radiation cured polymeric material having the combination of
properties of: (e) a glass transition temperature of above
40.degree. C.; and (f) a modulus of elasticity of greater than 25
MPa measured at 100.degree. C.; and wherein the ratio of the change
in length of said inner primary coating composition, after
radiation cure, to the change in length of said outer primary
coating composition, after radiation cure, is less than 2 when said
cured compositions are heated from 25.degree. C. to stripping
temperature.
17. The radiation-curable inner primary coating composition of
claim 5 or 13 wherein at least one oligomer is a radiation curable
oligomer comprising: at least one glass coupling moiety; at least
one slip agent moiety; and at least one radiation-curable
moiety.
18. The system of claim 6 or 14 wherein at least one oligomer in
said inner primary coating composition is a radiation curable
oligomer comprising: at least one glass coupling moiety; at least
one slip agent moiety; and at least one radiation-curable
moiety.
19. The coated optical glass fiber of claim 7 or 15 wherein said
inner primary coating is comprised of a cured radiation-curable
inner primary coating composition wherein at least one oligomer is
a radiation curable oligomer comprising: at least one glass
coupling moiety; at least one slip agent moiety; and at least one
radiation-curable moiety.
20. The ribbon assembly of claim 8 or 16 wherein said inner primary
coating is comprised of a cured radiation-curable inner primary
coating composition wherein at least one oligomer is a radiation
curable oligomer comprising: at least one glass coupling moiety; at
least one slip agent moiety; and at least one radiation-curable
moiety.
21. The radiation-curable inner primary coating composition of
claim 5 or 13 additionally comprising a soluble wax that is soluble
in said inner primary coating composition.
22. The system of claim 6 or 14 wherein said inner primary coating
composition additionally comprises a soluble wax that is soluble in
said inner primary coating composition.
23. The coated optical glass fiber of claim 7 or 15 wherein said
inner primary coating is comprised of a cured radiation-curable
inner primary coating composition containing a soluble wax that is
soluble in said inner primary coating.
24. The ribbon assembly of claim 8 or 16 wherein said inner primary
coating is comprised of a cured radiation-curable inner primary
coating composition containing a soluble wax that is soluble in
said inner primary coating.
25. The radiation-curable inner primary coating composition of
claim 5 or 13 wherein at least one oligomer is a radiation-curable
silicone oligomer comprising: a silicone compound; and at least one
radiation-curable moiety.
26. The system of claim 6 or 14 wherein at least one oligomer in
said inner primary coating composition is a radiation-curable
silicone oligomer comprising: a silicone compound; and at least one
radiation-durable moiety.
27. The coated optical glass fiber of claim 7 or 15 wherein said
inner primary coating is comprised of a cured radiation-curable
inner primary coating wherein at least one oligomer is a
radiation-curable silicone oligomer comprising: a silicone
compound; and at least one radiation-durable moiety.
28. The ribbon assembly of claim 8 or 16 wherein said inner primary
coating is comprised of a cured radiation-curable inner primary
coating composition wherein at least one oligomer is a
radiation-curable silicone oligomer comprising: a silicone
compound; and at least one radiation-durable moiety.
29. The radiation-curable inner primary coating composition of
claim 5 or 13 additionally containing a non-radiation-curable
silicone compound.
30. The system of claim 6 or 14 wherein said inner primary coating
composition additionally contains a non-radiation-curable silicone
compound.
31. The coated optical glass fiber of claim 7 or 15 wherein said
inner primary coating is comprised of a cured radiation-curable
inner primary coating composition containing a
non-radiation-curable silicone compound.
32. The ribbon assembly of claim 8 or 16 wherein said inner primary
coating is comprised of a cured radiation-curable inner primary
coating composition containing a non-radiation-curable silicone
compound.
33. The radiation-curable inner primary coating composition of
claim 5 or 13 wherein said composition comprises a fluorinated.
component selected from the group consisting of a radiation-curable
fluorinated oligomer, a radiation-curable fluorinated monomer and a
non-radiation curable fluorinated compound.
34. The system of claim 6 or 14 wherein said inner primary coating
composition comprises: a fluorinated component selected from the
group consisting of a radiation-curable fluorinated oligomer, a
radiation-curable fluorinated monomer and a non-radiation curable
fluorinated compound.
35. The coated optical glass fiber of claim 7 or 15 wherein said
inner primary coating comprises a fluorinated component selected
from the group consisting of a radiation-curable fluorinated
oligomer, a radiation-curable fluorinated monomer and a
non-radiation curable fluorinated compound.
36. The ribbon assembly of claim 8 or 16 wherein said inner primary
coating is comprises a fluorinated component selected from the
group consisting of a radiation-curable fluorinated oligomer, a
radiation-curable fluorinated monomer and a non-radiation curable
fluorinated compound.
37. The radiation-curable inner primary coating composition of
claim 5 or 13 wherein at least one oligomer is a radiation curable
oligomer comprising: at least one terminal linear moiety.
38. The system of claim 6 or 14 wherein at least one oligomer in
said inner primary coating composition is a radiation curable
oligomer comprising: at least one terminal linear moiety.
39. The coated optical glass fiber of claim 7 or 15 wherein said
inner primary coating is comprised of a cured radiation-curable
inner primary coating composition wherein at least one oligomer is
a radiation curable oligomer comprising: at least one terminal
linear moiety.
40. The ribbon assembly of claim 8 or 16 wherein said inner primary
coating is comprised of a cured radiation-curable inner primary
coating composition wherein at least one oligomer is a radiation
curable oligomer comprising: at least one terminal linear
moiety.
41. The radiation-curable inner primary coating composition of
claim 5 or 13 additionally containing a solid lubricant.
42. The system of claim 6 or 14 wherein said inner primary coating
composition additionally contains a solid lubricant.
43. The coated optical glass fiber of claim 7 or 15 wherein. said
inner primary coating is comprised of a cured radiation-curable
inner primary coating composition containing a solid lubricant.
44. The ribbon assembly of claim 8 or 16 wherein said inner primary
coating is comprised of a cured radiation-curable inner primary
coating composition containing a solid lubricant.
45. The radiation-curable inner primary coating composition of
claim 5 or 13 wherein at least one oligomer is substantially
linear.
46. The system of claim 6 or 14 wherein at least one oligomer in
said inner primary coating composition is substantially linear.
47. The coated optical glass fiber of claim 7 or 15 wherein said
inner primary coating is comprised of a cured radiation-curable
inner primary coating composition wherein at least one oligomer is
substantially linear.
48. The ribbon assembly of claim 8 or 16 wherein said inner primary
coating is comprised of a cured radiation-curable inner primary
coating composition wherein at least one S oligomer is
substantially linear.
49. The radiation-curable inner primary coating composition of
claim 5 or 13 wherein at least one oligomer is a urethane oligomer
having at least one polymeric block linked to at least one
functional group capable of polymerizing under the influence of
radiation via a urethane group, wherein the concentration of said
urethane groups is about 4% by weight or less, based on the total
weight of said inner primary coating composition.
50. The system of claim 6 or 14 wherein at least one oligomer is a
urethane oligomer having at least one polymeric block linked to at
least one functional group capable of polymerizing under the
influence of radiation via a urethane group, wherein the
concentration of said urethane groups is about 4% by weight or
less, based on the total weight of said inner primary coating
composition.
51. The coated optical glass fiber of claim 7 or 15 wherein said
inner primary coating is comprised of a cured radiation-curable
inner primary coating composition wherein at least one oligomer is
a urethane oligomer having at least one polymeric block linked to
at least one functional group capable of polymerizing under the
influence of radiation via a urethane group, wherein the
concentration of said urethane groups is about 4% by weight or
less, based on the total weight of said inner primary coating.
52. The ribbon assembly of claim 8 or 16 wherein said inner primary
coating is comprised of a cured radiation-curable inner primary
coating composition wherein at least one oligomer is a urethane
oligomer having at least one polymeric block linked to at least one
functional group capable of polymerizing under the influence of
radiation via a urethane group, wherein the concentration of said
urethane groups is about 4% by weight or less, based on the total
weight of said inner primary coating.
53. The radiation-curable inner primary coating composition of
claim 5 or 13 wherein at least one oligomer is comprised of at
least one polymeric block linked to at least one functional group
capable of polymerizing under the influence of radiation via a
linking group, and wherein said at least one polymeric block has a
calculated molecular weight of at least about 2000.
54. The system of claim 6 or 14 wherein at least one oligomer is
comprised of at least one polymeric block linked to at least one
functional group capable of polymerizing under the influence of
radiation via a linking group, and wherein said at least one
polymeric block has a calculated molecular weight of at least about
2000.
55. The coated optical glass fiber of claim 7 or 15 wherein said
inner primary coating is comprised of a cured radiation-curable
inner primary coating composition wherein at least one oligomer is
comprised of at least one polymeric block linked to at least one
functional group capable of polymerizing under the influence of
radiation via a linking group, and wherein said at least one
polymeric block has a calculated molecular weight of at least about
2000.
56. The ribbon assembly of claim 8 or 16 wherein said inner primary
coating is comprised of a cured radiation-curable inner primary
coating composition wherein at least one oligomer is comprised of
at least one polymeric block linked to at least one functional
group capable of polymerizing under the influence of radiation via
a linking group, and wherein said at least one polymeric block has
a calculated molecular weight of at least about 2000.
57. The radiation-curable inner primary coating composition of
claim 5 or 13 containing an oligomer and a monomer diluent, and
wherein said oligomer and monomer diluent have a high aromatic
content.
58. The system of claim 6 or 14 wherein the inner primary coating
composition contains an oligomer and a monomer diluent, and wherein
said oligomer and monomer diluent have a high aromatic content.
59. The coated optical glass fiber of claim 7 or 15 wherein said
inner primary coating is comprised of a cured radiation-curable
inner primary coating containing an oligomer and a monomer diluent,
and wherein said oligomer and monomer diluent have a high aromatic
content.
60. The ribbon assembly of claim 8 or 16 wherein said inner primary
coating is comprised of a cured radiation-curable inner primary
coating an oligomer and a monomer diluent, and wherein said
oligomer and monomer diluent have a high aromatic content.
61. A radiation-curable composite oligomer having: at least one
glass coupling moiety; at least one slip agent moiety; and at least
one radiation-curable moiety capable of polymerizing under the
influence of radiation; wherein said glass coupling moiety, slip
agent moiety and radiation-curable functional group are each
covalently linked to form said composite oligomer.
62. The radiation-curable composite oligomer of claim 61 wherein
said glass coupling moiety is comprised of a silane moiety, said
slip agent moiety is comprised of a siloxane moiety, and said
radiation-curable moiety is comprised of an ethylenically
unsaturated moiety.
63. A radiation-curable inner primary coating composition for an
optical glass fiber comprising an oligomer having at least one
functional group capable of polymerizing under the influence of
radiation, and additionally comprising a radiation-curable
composite oligomer having: at least one glass coupling moiety; at
least one slip agent moiety; and at least one radiation-curable
moiety capable of polymerizing under the influence of radiation;
wherein said glass coupling moiety, slip agent moiety and said
radiation-curable functional group are each covalently linked to
form said composite oligomer.
64. The radiation-curable inner primary coating composition of
claim 63 wherein said glass coupling moiety is comprised of a
silane moiety, said slip agent moiety is comprised of a siloxane
moiety, and said radiation-curable moiety is comprised of an
ethylenically unsaturated moiety.
65. A radiation-curable inner primary coating composition for an
optical glass fiber comprising an oligomer having at least one
functional group capable of polymerizing under the influence of
radiation, and additionally comprising a silicone compound
containing at least one radiation-curable functional group bound
near a terminus of said compound, capable of copolymerizing with
said radiation-curable oligomer under the influence of
radiation.
66. The radiation-curable inner primary coating composition of
claim 65 wherein said silicone compound is a silicone acrylate.
67. A radiation-curable inner primary coating composition for an
optical glass fiber comprising an oligomer having at least one
functional group capable of polymerizing under the influence of
radiation, said composition additionally comprising a fluorinated
component selected from the group consisting of a radiation-curable
fluorinated oligomer, a radiation-curable fluorinated monomer and a
non-radiation curable fluorinated compound.
68. The radiation-curable inner primary coating composition of
claim 67 additionally comprising a silicone component selected from
the group consisting of a radiation-curable silicone oligomer, a
radiation-curable silicone monomer and a radiation-curable silicone
compound and a non-radiation curable silicone compound.
69. A radiation-curable inner primary coating composition for an
optical glass fiber comprising an oligomer having at least one
functional group capable of polymerizing under the influence of
radiation, said composition additionally comprising a solid
lubricant.
70. A radiation-curable inner primary coating composition for an
optical glass fiber comprising an oligomer having at least one
functional group capable of polymerizing under the influence of
radiation, wherein at least one said oligomer is comprised of a
polymeric block linked to said functional group via a urethane
group, and the concentration of said urethane groups is about 4% by
weight or less, based on the total weight of said composition.
71. A radiation-curable inner primary coating composition for an
optical glass fiber comprising an oligomer having at least one
functional group capable of polymerizing under the influence of
radiation, wherein at least one said oligomer is comprised of a
polymer block linked to said functional group via a linking group,
and said polymeric block has a calculated molecular weight of at
least about 3100.
72. A radiation-curable inner primary coating composition for an
optical glass fiber comprising an oligomer and a monomer diluent
having at least one functional group capable of polymerizing under
the influence of radiation, wherein said oligomer and monomer
diluent have a high aromatic content.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part application of
co-pending U.S. patent application Ser. No. 08/877,585, filed Jun.
17, 1997, which is itself a continuation-in-part application of
co-pending U.S. patent application Ser. No. 08/840,893, filed on
Apr. 17, 1997, which is itself a continuation-in-part application
of U.S. patent application Ser. No. 08/745,790 filed on Nov. 8,
1996, all of which are hereby incorporated in their entirety-by
reference.
FIELD OF THE INVENTION
[0002] The invention relates to radiation-curable inner and outer
primary optical glass fiber coating compositions. The invention
also relates to coated optical glass fibers and optical glass fiber
assemblies. More particularly, the invention relates to a ribbon
assembly having improved ribbon stripping capabilities.
BACKGROUND OF THE INVENTION
[0003] Optical glass fibers are usually coated with two superposed
radiation-cured coatings, which together form a primary coating.
The coating which contacts the glass surface is called the inner
primary coating and the overlaying coating is called the outer
primary coating.
[0004] The inner primary coating is usually a soft coating having a
low glass transition temperature (hereinafter "Tg"), to provide
resistance to microbending. Microbending can lead to attenuation of
the signal transmission capability of the coated optical glass
fiber and is therefore undesirable. The outer primary coating is
typically a harder coating providing desired resistance to handling
forces, such as those encountered when the coated fiber is
cabled.
[0005] For the purpose of multi-channel transmission, optical glass
fiber assemblies containing a plurality of coated optical fibers
have been used. Examples of optical glass fiber assemblies include
ribbon assemblies and cables. A typical optical glass fiber
assembly is made of a plurality of coated optical glass fibers
which are bonded together in a matrix material. For example, the
matrix material can encase the optical glass fibers, or the matrix
material can edge-bond the optical glass fibers together.
[0006] Optical glass fiber assemblies provide a modular design
which simplifies the construction, installation and maintenance of
optical glass fibers by eliminating the need to handle individual
optical glass fibers.
[0007] Coated optical glass fibers for use in optical glass fiber
assemblies are usually coated with an outer colored layer, called
an ink coating, or alternatively a colorant is added to the outer
primary coating to facilitate identification of the individual
coated optical glass fibers. Such ink coatings and colored outer
primary coatings are well known in the art. Thus, the matrix
material which binds the coated optical glass fibers together
contacts the outer ink layer if present, or the colored outer
primary coating.
[0008] When a single optical glass fiber of the assembly is to be
fusion connected with another optical glass fiber, or with a
connector, an end part of the matrix layer can be removed to
separate each of the optical glass fibers.
[0009] Desirably, the primary coatings on the coated optical glass
fibers, and the ink coating if present, are removed simultaneously
with the matrix material to provide bare portions on the surface of
the optical glass fibers (hereinafter referred to as "ribbon
stripping"). In ribbon stripping, the matrix material, primary
coatings, and ink coating, are desirably removed as a cohesive unit
to provide a clean, bare optical glass fiber which is substantially
free of residue. This residue can interfere with the optical glass
fiber ribbon mass fusion splicing operation, and therefore usually
must be removed by wiping prior to splicing. However, the step of
removing the residue can cause abrasion sites on the bare optical
glass fiber, thus compromising the strength of the connection. The
superior stripping functionality of ribbon assemblies to provide
clean, residue-free, bare optical glass fibers during ribbon
stripping according to this invention has heretofore been believed
to be unobtainable.
[0010] A common method for practicing ribbon stripping at a
terminus of the ribbon assembly is to use a heated stripping tool.
Such a tool consists of two plates provided with heating means for
heating the plates to about 90 to about 120 C. An end section of
the ribbon assembly is pinched between the two heated plates and
the heat of the tool softens the matrix material and the primary
coatings on the individual optical glass fiber. The heat-softened
matrix material and heat-softened primary coatings present on the
individual optical glass fibers can then be removed to provide bare
optical glass fiber ends, at which the fusion connections can be
made. A knife cut is often used to initiate a break in the matrix
material to the inner primary coating. Typically, only about a 1 to
4 cm section of the matrix material and coatings on the optical
glass fibers need be removed. Identification of the bare individual
optical glass fibers achieved by tracing back along the bare
optical fiber until the ink coating or colored outer primary
coating is seen.
[0011] U.S. Pat. No. 5,373,578 discloses a ribbon assembly
containing a plurality of coated optical glass fibers. Each of the
optical glass fibers is coated with an inner primary coating which
is adjacent to the optical glass fiber, with an outer primary
coating and an ink coating on the outer primary coating. The inner
primary coating is modified so that adhesion between the inner
primary coating and the optical glass fiber is reduced. This
reduction in adhesion facilitates easy removal of the heat-softened
primary coating when using a heat stripping method. While this
patent. discloses, at column 5, lines 10-13, that the adhesion
between the inner primary coating and the optical glass fiber
should be sufficient to prevent delamination of the inner primary
coating from the optical glass fiber, any reduction in the adhesion
between the inner primary coating and the optical glass fiber
increases the possibility of such undesirable delamination,
especially in the presence of moisture. Delamination of the inner
primary coating from the optical glass fiber can lead to degraded
strength of the optical glass fiber as well as signal transmission
attenuation disadvantages.
[0012] Published European patent application 0262340 discloses a
ribbon cable having a "peel layer" as the outermost coating layer
on each of optical glass fibers contained within the ribbon cable.
During ribbon stripping, the peel layer is destroyed and the matrix
material is removed from the coated optical glass fibers. However,
after ribbon stripping, the optical glass fibers are still coated
with the primary coatings. That is, the primary coatings are not
simultaneously removed with the matrix material in the ribbon
assemblies disclosed in this publication.
[0013] U.S. Pat. No. 5,011,260 discloses a ribbon cable having a
"decoupling layer" disposed between the coated optical glass fibers
and the matrix material. In this manner, the matrix material may be
easily removed from the coated optical glass fibers by application
of low stripping force. This patent includes a general statement
that the coatings on the optical glass fiber can be simultaneously
removed with the matrix material during ribbon stripping. However,
this patent fails to teach how to solve the problems associated
with the residues remaining on the bare optical glass fibers after
ribbon stripping conventional ribbon assemblies.
[0014] Published European patent application 0407004 discloses a
ribbon cable containing a matrix material having sufficient
adhesion to the ink coated optical glass fibers to remain adhered
thereto during normal use but is easily strippable therefrom
without damaging the integrity of the ink layer on the coated
optical glass fibers. Thus, the ribbon assembly disclosed in this
publication does not have the capability of removing the primary
coatings on the optical glass fibers simultaneously with removal of
the matrix material during ribbon stripping, so as to provide
residue-free bare optical glass fibers.
[0015] Published European patent application 0527266 discloses a
ribbon cable containing a lubricating "interfacial layer" which
separates the matrix material from the coated optical glass fibers.
The interfacial layer facilitates easy removal of the matrix
material from the coated optical glass fibers. While this
publication discloses at page 3, line 15, that the buffer layer and
first protective coating can be stripped in one step, there is no
disclosure teaching how to accomplish such an operation.
Furthermore, the lubricating interfacial layer will inhibit
simultaneous removal of the first protective coating with the
matrix material. Thus, this publication does not teach how to make
a ribbon assembly having the capability of removing the primary
coatings on the optical glass fibers simultaneously with the matrix
material during ribbon stripping, so as to provide residue-free
bare optical glass fibers.
[0016] U.S. Pat. No. 4,900,126 discloses a ribbon cable in which
the bonding adhesive forces between the ink layer and the primary
coatings on the optical glass fibers are greater than the bonding
between the ink layer and the matrix material. In this manner, the
matrix material can be easily removed from the ink coated optical
glass fibers without removing the ink layer. However, this patent
does not address the problems associated with removing the primary
coating layers simultaneously with the matrix material.
[0017] U.S. Pat. No. 4,660,927 teaches a silicone-coated optical
fiber in which the soft silicone coating is easily peeled from the
surface of the optical glass fibers by finger pressure. The coating
contains a first siloxane component having aliphatic unsaturated
groups and a second siloxane component having mercaptoalkyl groups.
Because such a coating is easily peelable, as by rubbing with
finger pressure, the coating has insufficient adhesion to the
surface of the optical glass fibers to prevent delamination during
most uses. Furthermore, this patent does not address the problems
of ribbon stripping, but rather only the stripping of a single
optical glass fiber. It is generally known that three coating
systems (inner primary coating, outer primary coating, and ink
coating) having acceptable single fiber strippability will exhibit
dramatically different levels of strippability characteristics when
used in ribbon form.
[0018] U.S. Pat. No. 4,496,210 provides a radiation-curable optical
fiber coating composition containing a polysiloxane. However, this
patent does not address the problems associated with ribbon
stripping.
[0019] Japanese Patent Application H3-35210 teaches to combine a
liquid lubricant, such as liquid silicone oil or liquid aliphatic
oil, with a mercaptosilane compound in an inner primary coating
composition. During stripping, when the bond between the surface of
the optical glass fiber and inner primary coating is broken the
liquid lubricant invades the boundary between the surface of the
optical glass fiber and the inner primary coating. The liquid
lubricant must not have a high compatibility with the inner primary
coating or it will not bleed out of the inner primary coating
during stripping. However, this document fails to teach a system to
adjust the level of fiber friction between the adjacent surfaces of
the optical glass fiber and the inner primary coating to a level
which provides a resistive force that is less than the cohesive
strength of the inner primary coating. Thus, while this document
teaches that the inner primary coating can be stripped more easily
by incorporating liquid lubricant compounds, the inner primary
coating will still leave unwanted residue on the surface of the
optical glass fiber if the above described fiber friction forces
are at a level which provide a resistive force that is greater than
the cohesive strength of the inner primary coating.
[0020] One primary coating composition available from JSR
Corporation, designated as R-1055, is specified as having, inter
alia, a viscosity of 5000 cps @25.degree. C., a glass transition
temperature of -4.degree. C., a shrinkage value of 2.9%, a tensile
strength value of 0.21 kg/mm.sup.2, a tensile elongation value of
195%, an adhesion force of 20 g/cm and a Young's modulus
@23.degree. C. of 0.12 kg/mm.sup.2. When this composition was
tested in accordance with the test methods herein, it had a
measured crack propagation value of 1.56 mm (standard deviation
0.2), and a fiber pull-out friction value of 26.3 g/mm (standard
deviation 1.65).
[0021] There are many test methods which may be used to determine
the performance of a ribbon assembly during ribbon stripping. An
example of a suitable test method for determining the stripping
performance of a ribbon is disclosed in the article by Mills, G.,
"Testing of 4- and 8-fiber ribbon strippability", 472 International
Wire & Cable Symposium Proceedings (1992), the complete
disclosure of which is incorporated herein by reference.
[0022] Many attempts have been made to understand the problems
associated with ribbon stripping and to find a solution to increase
ribbon stripping performance. The following publications attempt to
explain and solve the problems associated with ribbon stripping: K.
W. Jackson, et. al., "The Effect of Fiber Ribbon Component
Materials on Mechanical and Environmental Performance", 28
International Wire & Symposium Proceedings (1993); H. C.
Chandon, et. al., "Fiber Protective Design for Evolving
Telecommunication Applications", International Wire & Symposium
Proceedings (1992); J. R. Toler, et. al., "Factors Affecting
Mechanical Stripping of Polymer Coatings From Optical Fibers",
International Wire. & Cable Symposium Proceedings (1989); and
W. Griffioen, "Strippability of Optical Fibers", EFOC & N,
Eleventh Annual Conference, Hague (1993).
[0023] The ability of a ribbon assembly to ribbon strip cleanly so
as to provide bare optical glass fibers that are substantially free
of residue is still unpredictable and the factors affecting ribbon
stripping are not fully understood. There is still a need for an
understanding of how the problems of ribbon stripping occur and a
solution to these problems.
SUMMARY OF THE INVENTION
[0024] It is an objective of the present invention to provide a
novel ribbon assembly having improved ribbon stripping
capabilities. It is another objective of the present invention to
provide a novel ribbon assembly which after ribbon stripping
provides bare optical glass fibers which are substantially free of
residue, that must be removed prior to forming connections to the
respective selected bare optical fibers.
[0025] Surprisingly, the above objects and other objects are and
have been obtained by the following. The present invention provides
a novel ribbon assembly comprising:
[0026] a plurality of coated optical glass fibers, at least one
optical glass fiber coated with at least an inner primary coating
and an outer primary coating, and optionally an ink coating;
and
[0027] a matrix material bonding said plurality of coated optical
glass fibers together, wherein said inner primary coating is
adapted to provide the combination of properties of:
[0028] (i) sufficient adhesion to said optical glass fiber to
prevent delamination during handling and in the presence of
moisture; and
[0029] (ii) a fiber friction force between said optical glass fiber
and said inner primary coating which has been so adjusted as to
allow the inner primary coating to slide readily off from the
optical glass fiber while leaving substantially no residue on the
surface of said optical glass fiber during ribbon stripping, when a
stripping force which is less than the cohesive strength of said
inner primary coating is applied to said ribbon assembly.
[0030] Also provided is a novel ribbon assembly comprising:
[0031] a plurality of optical glass fibers, at least one coated
optical glass fiber coated with at least an inner primary coating
and an outer primary coating, and optionally an ink coating;
and
[0032] a matrix material bonding said coated optical glass fibers
together,
[0033] and wherein said inner primary coating is adapted to provide
a fiber pull-out friction of about 30 grams/millimeter or less at a
rate of about 0.1 mm/sec in combination with a crack propagation
characteristic of at least about 1 millimeter at a rate of 0.1
mm/sec.
[0034] The present invention further provides a coated optical
glass fiber comprising:
[0035] an optical glass fiber;
[0036] an inner primary coating on the surface of said optical
glass fiber;
[0037] an outer primary coating substantially co-extensive with the
external surface of said inner primary coating, wherein said inner
and outer primary coatings are so formulated and selected so as to
provide a ratio of (i) the change in length of the inner primary
coating from an ambient temperature to a ribbon stripping
temperature to (ii) the change in length of the outer primary
coating from said ambient temperature to said ribbon stripping
temperature of less than about 1.5:1; and
[0038] optionally an ink coating adjacent to said outer primary
coating.
[0039] The invention further relates to a ribbon assembly
containing at least one of these coated optical glass fibers.
[0040] The present invention further relates to a novel
radiation-curable oligomer which can be used to adjust the fiber
friction to a level such that the resulting adhesive resistive
force level is less than the cohesive strength of the inner primary
coating. The novel radiation-curable oligomer comprises:
[0041] at least one glass coupling moiety;
[0042] at least one slip agent moiety; and
[0043] at least one radiation-curable moiety, wherein said glass
coupling, glass adhesion, and radiation curable moieties are each
covalently linked to said oligomer.
[0044] Also provided is a radiation-curable, inner primary coating
composition containing the composite oligomer, a coated optical
glass fiber made from the coating composition, and a ribbon
assembly containing at least one such coated optical glass
fiber.
[0045] The present invention also provides a radiation-curable,
inner primary coating composition comprising at least one
radiation-curable oligomer or monomer and a wax. Preferably, the
wax is present in an amount sufficient to provide a fiber friction
between an inner primary coating formed from said coating and an
optical glass fiber such that there is exhibited a resistive force
that is less than the cohesive strength of said coating formed from
said composition. The invention also provides a coated optical
glass fiber having an inner primary coating which contains a wax,
and a ribbon assembly which contains at least one such coated
optical glass fiber.
[0046] The present invention further provides a coated optical
glass fiber having an inner primary coating which has been
formulated from a radiation-curable, inner primary coating
composition containing a radiation-curable silicone oligomer or a
silicone compound. Preferably, the radiation-curable silicone
oligomer or silicone compound is present in an amount sufficient to
provide a fiber friction between the inner primary coating and the
optical glass fiber such that there is exhibited a resistive force
which is less than the cohesive strength of the inner primary
coating. The invention also provides a ribbon assembly which
contains at least one such coated optical glass fiber.
[0047] The present invention also provides a coated optical glass
fiber having an inner primary coating which has been formulated
from a radiation-curable, inner primary coating composition
containing a radiation-curable fluorinated oligomer or a
fluorinated compound. Preferably, the radiation-curable fluorinated
oligomer or fluorinated compound is present in an amount sufficient
to provide a fiber friction between the inner primary coating and
the optical glass fiber such that there is exhibited a resistive
force that is less than the cohesive strength of the inner primary
coating. The invention further provides a ribbon assembly which
contains at least one such coated optical glass fiber.
[0048] The present invention also provides a radiation-curable,
inner primary coating composition comprising at least one
radiation-curable oligomer or monomer and a solid lubricant which
is substantially insoluble in the composition. Preferably, the
solid lubricant is present in an amount sufficient to provide a
fiber friction between an inner primary coating formed from said
coating and an optical glass fiber such that there is exhibited a
resistive force which is less than the cohesive strength of said
coating formed from said composition. The invention also provides a
coated optical glass fiber having an inner primary coating which
contains a solid lubricant, and a ribbon assembly which contains at
least one such coated optical glass fiber.
[0049] The present invention further provides a ribbon assembly
comprising a plurality of coated optical glass fibers, at least one
optical glass fiber coated with at least an inner primary coating
and an outer primary coating, and optionally an ink coating, and a
matrix material bonding said plurality of coated optical glass
fibers together. The inner primary coating is formulated from a
radiation-curable inner primary coating composition containing at
least one radiation-curable urethane oligomer comprising at least
one polymeric block and at least one functional group capable of
polymerization in the presence of actinic radiation connected to
said at least one polymeric block. The coating composition has a
concentration of urethane groups which is selected to provide said
inner primary coating with a fiber friction force level between
said optical glass fiber and said inner primary coating in
combination with a crack propagation level that provides the inner
primary coating with the functional capability of sliding off of
the optical glass fiber and leaving substantially no residue on the
surface of said optical glass fiber during ribbon stripping when a
stripping force which is less than the cohesive strength of said
inner primary coating is applied to said ribbon assembly.
[0050] The present invention further provides a ribbon assembly
comprising a plurality of coated optical glass fibers, at least one
optical glass fiber coated with at least an inner primary coating
and an outer primary coating, and optionally an ink coating, and a
matrix material bonding said plurality of coated optical glass
fibers together. The inner primary coating is formulated from a
radiation-curable inner primary coating composition containing at
least one radiation-curable oligomer comprising at least one
polymeric block and at least one functional group capable of
polymerization in the presence of actinic radiation connected to
said at least one polymeric block. The polymeric block has a
molecular weight which is selected to provide said inner primary
coating with a fiber friction force level between said optical
glass fiber and said inner primary coating in combination with a
crack propagation level that provides the inner primary coating
with the functional capability of sliding off of the optical glass
fiber and leaving substantially no residue on the surface of said
optical glass fiber during ribbon stripping when a stripping force
which is less than the cohesive strength of said inner primary
coating is applied to said ribbon assembly.
[0051] The invention also provides a radiation-curable, inner
primary coating composition formulated from a composition
comprising at least one urethane oligomer having at least one
polymeric block and at least one functional group capable of
polymerization in the presence of actinic radiation connected to
said at least one polymeric block. The coating composition has a
concentration of urethane groups that is so selected to provide
said inner primary coating with a fiber friction force level
between an optical glass fiber and an inner primary coating formed
from said coating composition in combination with a crack
propagation level which provides the inner primary coating with the
functional capability of sliding off the optical glass fiber and
leaving substantially no residue on the surface of said optical
glass fiber during ribbon stripping when a stripping force which is
less than the cohesive strength of said inner primary coating is
applied to said inner primary coating.
[0052] The present invention further provides a radiation-curable,
inner primary optical glass fiber coating composition formulated
from a composition comprising at least one radiation-curable
oligomer having at least one polymeric block and at least one
functional group capable of polymerization in the presence of
actinic radiation connected to said at least one polymeric block.
The polymeric block has a molecular weight so selected to provide
said inner primary coating with a fiber friction force level
between said optical glass fiber and said inner primary coating in
combination with a crack propagation level that provides the inner
primary coating with the functional capability of sliding off the
optical glass fiber and leaving substantially no residue on the
surface of said optical glass fiber during ribbon stripping when a
stripping force which is less than the cohesive strength of said
inner primary coating is applied to said inner primary coating.
[0053] The present invention also provides coated optical glass
fibers containing at least one inner primary coating formed from
the above radiation-curable, inner primary coating
compositions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] FIG. 1 illustrates a longitudinal cross-sectional view of a
coated optical glass fiber.
[0055] FIG. 2 illustrates a representative graph of the normalized
strip force required to slide an optical fiber ribbon coating
composite along the surface of an optical glass fiber.
[0056] FIG. 3 illustrates the ratchet effect of an inner primary
coating sliding off an optical glass fiber during ribbon
stripping.
[0057] FIG. 4 is a graph of the change in length L ("dL") for a
commercially available outer primary coating as the temperature is
increased.
[0058] FIG. 5 illustrates a partial cross-sectional view of a
coated optical glass fiber.
[0059] FIG. 6 illustrates a hypothetical contour plot for
determining the predicted strip cleanliness.
[0060] FIG. 7 illustrates a graph of the fiber pull-out friction
versus urethane concentration.
[0061] FIG. 8 illustrates a graph of the fiber pull-out friction
versus urethane concentration.
[0062] FIG. 9 illustrates a graph of the fiber pull-out friction
versus urethane concentration.
[0063] FIG. 10 illustrates a graph of the fiber pull-out friction
versus urethane concentration.
[0064] FIG. 11 illustrates a graph of the fiber pull-out friction
versus urethane concentration.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0065] The invention will now be explained in detail with reference
to the attached drawings.
[0066] Based on extensive experimentation, it is now believed that
ribbon stripping functionally involves two phases, a first adhesion
breaking phase and a second frictive sliding phase. This can be
characterized by the following equation (1):
F.sub.stripping=F.sub.adhesive+F.sub.friction (1)
[0067] where
[0068] F.sub.stripping is the stripping force applied to the inner
primary coating;
[0069] F.sub.adhesive is the force required to break the adhesive
forces between the optical glass fiber and the inner primary
coating; and
[0070] F.sub.friction is a function of the normal force the inner
primary coating exerts against the surface of the optical glass
fiber and the coefficient of friction of the inner primary
coating.
[0071] F.sub.friction is equal to F.sub.static, defined as the
condition when the inner primary coating is in a static position,
and F.sub.friction is equal to F.sub.kinetic defined as when the
inner primary coating is in motion relative to the optical glass
fiber.
[0072] During the adhesion breaking phase, the adhesive force
between the inner primary coating and the surface of the optical
glass fiber must be broken to delaminate the inner primary coating
from the surface of the optical glass fiber. Once that adhesive
force is broken, and the inner primary coating is delaminated from
the surface of the optical glass fiber, the fiber friction force
between the inner primary coating and the surface of the optical
glass fiber must then be overcome to remove the inner and outer
primary coatings, along with the matrix material, from the optical
glass fiber.
[0073] The adhesive force between the inner primary coating and the
surface of the optical glass fiber is generally increased by an
increase in the following:
[0074] (1) covalent bonding, for example from glass adhesion
promoters;
[0075] (2) weak molecular interactions, such as Van der Waal's
attractions, hydrogen-bonding, electrostatic, and the like;
[0076] (3) static coefficient of friction;
[0077] (4) surface energy of the inner primary coating and surface
energy of the optical glass fiber;
[0078] (5) surface roughness; and
[0079] (6) adhesive bonding area.
[0080] The adhesive force between the inner primary coating and the
surface of the optical glass fiber is generally decreased by an
increase in the temperature.
[0081] The fiber friction force between the inner primary coating
and the surface of the optical glass is generally increased by an
increase in one or more of the following:
[0082] (1) the normal force of the inner primary coating against
the surface of the optical glass fiber at the ribbon stripping
temperature;
[0083] (2) the static and kinetic coefficient of friction at the
ribbon stripping temperature;
[0084] (3) surface roughness; and
[0085] (4) frictive area.
[0086] The normal force includes weak molecular interactions, such
as Van der Waal's attractions, hydrogen-bonding, electrostatic, and
the like, between the surface of the optical glass fiber and the
inner primary coating. In general, the fiber friction force is
decreased with an increase in temperature.
[0087] The rigidity and integrity of the outer primary coating at
the ribbon stripping temperature can also affect the frictive
force. During ribbon stripping the outer primary coating, ink
coating, and other rigid coating layers, such as the matrix
material, provide the stiffening backbone which allows for intact
removal of the matrix material and inner and outer primary coatings
to provide a cohesive tube (hereinafter referred to as "coating
tube") If the rigidity and integrity are insufficient, the outer
primary coating can buckle during ribbon stripping, which can
significantly increase the fiber friction force and/or induce
shearing stresses causing integrity failure of the inner primary
coating resulting in undesirable residue on the surface of the
optical glass fiber.
[0088] Preferably, the adhesion between the matrix material and the
ink coating or colored outer primary coating is greater than the
adhesion between the inner primary coating and the surface of the
optical glass fiber to ensure that the inner primary coating
delaminates from the surface of the optical glass fiber during
ribbon stripping. Similarly, both the adhesion between the ink
coating and the outer primary coating, and the adhesion between
outer primary coating and the inner primary coating, should be
greater than the adhesion between the inner primary coating and the
surface of the optical glass fiber to ensure that the inner primary
coating delaminates from the surface of the optical glass fiber, as
well as to provide a cohesive coating tube during ribbon stripping.
Usually, the adhesion between the matrix material and the colored
outer primary coating or ink coating, as well as the adhesion
between each of the coating layers is sufficient to ensure
delamination of the inner primary coating from the surface of the
optical glass fiber during ribbon stripping because the matrix
material and coating layers mainly comprise organic materials. In
general, layers of materials having similar properties, such as an
adjacent organic layer/organic layer bond, tend to bond more easily
together than layers having dissimilar properties, such as an.
organic layer/inorganic layer bond.
[0089] FIG. 1 illustrates an optical glass fiber 7 coated with an
inner primary coating 8 and a commercially available outer primary
coating 9. The length of the inner primary coating in FIG. 1 shown
at 20 has been selected to be 35 mm because this is a typical
length of the coatings stripped from the ends of the optical glass
fibers during ribbon stripping. When a typical ribbon stripping
tool is applied to a ribbon assembly, pressure is applied to the
ribbon assembly between heated plates. At the ends of the plates
near the cut made in the matrix material and inner and outer
primary coatings, the inner primary coating can form an initial
delamination site on the optical glass fiber, shown at 27 and 28
(referred to as debond area). Because the areas 27 and 28 of the
inner primary coating are delaminated, they must be subtracted from
that area of the inner primary coating which is still bonded to the
surface of the optical glass fiber when measuring the adhesive
bonding area between the inner primary coating and the surface of
the optical glass fiber. The radius of the optical glass fiber is
62.5 microns, shown at 22. The radius of the outer surface of inner
primary coating is 95 microns, shown at 24. The radius of the outer
surface of the outer primary coating is 125 microns, shown at 26.
From FIG. 1, the adhesive bonding area is equal to the glass
surface area (13.744 mm.sup.2) minus the debond area. The frictive
area is the total glass surface area of the section to be stripped
during ribbon stripping (13.744 mm.sup.2).
[0090] It is believed that during ribbon stripping the inner
primary coating may ratchet off the optical glass fiber, as shown
in FIG. 2. FIG. 2 is a demonstration of the adhesive force and
fiber friction force being overcome by the stripping force applied
to the inner primary coating during the ribbon stripping process.
As stripping force is applied from the stripping tool to the inner
primary coating, the stripping force increases to a level at which
the adhesive force between the inner primary coating and the
surface of the optical glass fiber is overcome, which is shown at
1. At this level, the inner primary coating begins to delaminate
from the surface of the optical glass fiber. Then, the stripping
force decreases as the inner primary coating delaminates from the
optical glass fiber, shown generally at 2. Once delamination has
completed, shown at 3, the inner primary coating slides along the
surface of the optical glass fiber and the stripping force
decreases to the level shown at 4. As the inner primary coating is
being slid off of the optical glass fiber the stripping force
required to slide the inner primary coating against the optical
glass fiber ratchets between the higher static fiber friction force
and the lower kinetic fiber friction force.
[0091] The static fiber friction force is a function of the static
coefficient of friction of the inner primary coating and the normal
force of the inner primary coating against the optical glass fiber.
The kinetic fiber friction force is a function of the kinetic
coefficient of friction of the inner primary coating and the normal
force of the inner primary coating against the optical glass fiber.
The static fiber friction force resists initial sliding movement
and the kinetic fiber friction force resists subsequent sliding
movement. In other words, once the adhesive bond is broken and the
static fiber friction force is overcome, shown at 3, the inner
primary coating slides a set distance until the kinetic fiber
friction force prevents further motion and the inner primary
coating becomes momentarily stuck in place against the surface of
the optical glass fiber, shown at 4. As the stripping force
increases, and before the inner primary coating resumes its motion
relative to the optical glass fiber, the potential energy is stored
in the inner primary coating which produces a tensile force and a
stripping force within the inner primary coating. The tensile force
is opposed to the normal force and the stripping force is opposed
to the fiber friction force.
[0092] The motion force ("F.sub.motion") of the inner primary
coating is a vector sum of the tensile force ("F.sub.tensile") and
the stripping force ("F.sub.stripping"). The resistive force
("F.sub.resistive") is a vector sum of the fiber friction force
("F.sub.friction") and the normal force on the inner primary
coating against the surface of the optical glass fiber.
[0093] Once the motion force ("F.sub.motion") exceeds the resistive
force ("F.sub.resistive") the inner primary coating begins to
slide, shown at 5. The inner primary coating quickly slides a set
distance and then becomes momentarily stuck, shown at 6. The
distance the inner primary coating slides along the surface of the
optical glass fiber between the points 5 and 6 in FIG. 2 is
referred to as slip-stick distance. The slip-stick distance will
vary and be dependent upon the materials used in the inner primary
coating and optical glass fiber, and will also be dependent upon
random probability due to non-homogeneity in the inner primary
coating and optical glass fiber surface.
[0094] FIG. 3 further explains the ratcheting effect during ribbon
stripping by way of example. As shown in FIG. 3, a partial
longitudinal cross-section of an optical glass fiber is shown at 7.
A two-dimensional vector explanation will be used herein for ease
of explanation. However, it is understood that a coated optical
glass fiber is a three-dimensional object and all of the described
vectors need to be extended an additional dimension.
[0095] The optical glass fiber is coated with an inner primary
coating shown at 8, and an outer primary coating shown at 9. The
thickness "Y" of the inner primary coating is about 37.5 microns,
shown at 12. As stripping force is indirectly applied to the inner
primary coating in the direction shown at 10, the inner primary
coating is deformed a pre-slip distance "X", shown at 11, at which
point the inner primary coating delaminates and begins to ratchet
along the surface of the optical glass fiber. The stripping force
required to make the inner primary coating begin to ratchet along
the surface of the optical glass fiber can be calculated as
follows. The length of the tensile deformation of the deformed
inner primary coating at the level of strip force required to make
the inner primary coating begin to slide after being momentarily
stuck to the surface of the optical glass fiber "Z" is shown at 13.
The % elongation of the deformed inner primary coating can be
calculated from the values Z and Y using the following equation
(2):
(Z-Y)/Y=% elongation (2)
[0096] From a stress/strain curve, one skilled in the art can
readily use the % elongation to calculate the tensile force
(F.sub.tensile) required to initiate sliding of the inner primary
coating from a static position.
[0097] The vector for the static fiber friction force
F.sub.friction is shown at 19. When F.sub.motion is greater than
F.sub.resistive, the inner primary coating will begin to slide from
a static position. F.sub.motion, shown at 15, is the vector sum of
F.sub.tensile, shown at 14, and F.sub.stripping, shown at 16.
F.sub.resistive, shown at 17, is the vector sum of F.sub.friction,
shown at 19, and F.sub.normal, shown at 18.
[0098] If either of the vector components F.sub.stripping or
F.sub.tensile is greater than the corresponding inner primary
coating resistive vector components (shear strength and tensile
strength, respectively), then the inner primary coating will
cohesively fail during ribbon stripping leaving an undesirable
residue of inner primary coating material on the surface of the
optical glass fiber.
[0099] Similarly, if either of the vector components F.sub.friction
or F.sub.nornal is greater than the inner primary coating resistive
vector components (shear strength and tensile strength,
respectively), then the inner primary coating will cohesively fail
during ribbon stripping leaving an undesirable residue of inner
primary coating material on the surface of the optical glass
fiber.
[0100] More generally, the inner primary coating will cohesively
fail if F.sub.resistive is greater than the cohesive strength of
the inner primary coating. Thus, to prevent such residue, the
F.sub.friction and/or F.sub.normal should be so adjusted as to
provide a F.sub.resistive that is less than the cohesive strength
of the inner primary coating.
[0101] The term "cohesive strength" of the inner primary coating is
used herein to mean the amount of force necessary to destroy the
integrity of the inner primary coating. Thus, a higher cohesive
strength will require a greater amount of force to destroy the
integrity of the inner primary coating. The cohesive strength can
be measured using any one of (1) the shear strength of the inner
primary coating, (2) the tensile strength of inner primary coating,
or (3) the crack propagation of the inner primary coating.
Preferably, the cohesive strength is measured using the crack
propagation. test, as described herein below.
[0102] This residue can interfere with the optical glass fiber
ribbon mass fusion splicing operation, and therefore must be
removed prior to splicing by wiping. The step of removing the
residue can cause abrasion sites on the bare optical glass fiber,
thus compromising the strength of the connection.
[0103] Once the adhesive bonds have been broken and the inner
primary coating has been delaminated from the surface of the
optical glass fiber, the ability of a ribbon assembly to strip
cleanly during ribbon stripping and to provide bare optical glass
fibers which are substantially free of residue can be understood
using the following simplified equation (3):
F.sub.friction=C.sub.f.times.F.sub.normal (3)
[0104] where F.sub.friction is the static frictive force between
the inner primary coating and the optical glass fiber;
[0105] C.sub.f is the static coefficient of friction of the inner
primary coating on the surface of the optical glass fiber, and
[0106] F.sub.normal is the normal force of the inner primary
coating against the surface of the optical glass fiber.
[0107] Hereinafter, the use of the term "fiber friction" in the
specification and claims refers to the static fiber friction
force.
[0108] In general, the lower the fiber friction, the lower the
resistive force, and the easier the inner primary coating can be
removed from the surface of the optical glass fiber without leaving
a residue. From equation 3, it is evident that the fiber friction
can be reduced by decreasing either or both the static coefficient
of friction or the normal force.
[0109] Each inner primary coating has a specific cohesive strength
which maintains the integrity of the inner primary coating. The
greater the cohesive strength of the inner primary coating the
greater the amount of energy required to break apart or fracture
the inner primary coating. Thus, an inner primary coating having a
higher cohesive strength can withstand greater stripping forces
during ribbon stripping, without breaking apart and leaving residue
on the surface of the optical glass fiber, than an inner primary
coating having a lower cohesive strength.
[0110] From the above discussion, it is clear that if the fiber
friction is at a level which provides a resistive force that is
greater than the cohesive strength of the inner primary coating,
then the inner primary coating will break apart leaving residue on
the surface of the optical glass fiber. Thus, when selecting or
formulating the inner and outer primary coatings, the fiber
friction level should be adjusted taking into account the cohesive
strength of the inner primary coating so that fiber friction
provides resistive force that is less than the cohesive strength of
the inner primary coating.
[0111] Minimizing the Normal Force
[0112] From the above equations, the fiber friction force between
the optical glass fiber and inner primary coating can be lowered by
reducing the normal force of the inner primary coating against the
surface of the optical glass fiber. In general, the greater the
normal force, the greater the fiber friction force between the
optical glass fiber and the inner primary coating. In other words,
the harder the inner primary coating is pressing against the
surface of the optical glass fiber, the harder it will be to slide
the inner primary coating against the surface of the optical glass
fiber and the greater the chances of leaving residue from the inner
primary coating on the surface of the optical glass fiber. Since
the normal force is a component of the fiber friction, lowering the
normal force will lower the fiber friction. The normal force should
therefore be adjusted or selected so as to provide a normal force
vector component and a fiber friction vector component that
provides a vector sum (resistive force) which is less than the
cohesive strength of the inner primary coating.
[0113] During ribbon stripping, the inner primary and outer primary
coatings are heated, typically to about 90 C. to about 120 C.
Because inner primary coatings usually have a lower Tg than that of
outer primary coatings, inner primary coatings usually expand to a
greater extent than the outer primary coatings during ribbon
stripping. Thus, when the inner and outer primary coatings are
heated, the inner primary coating expands to a greater extent than
the outer primary coating causing a pressure build-up within the
inner primary coating and between the surface of the optical glass
fiber and the outer primary coating. This pressure buildup in the
inner primary coating increases the normal force of the inner
primary coating against the optical glass fiber, thereby increasing
the fiber friction force between the inner primary coating and the
surface of the optical glass fiber. Thus, the resistive force will
be increased by an increase in the normal force vector component
and an increase in the fiber friction vector component.
[0114] It is believed that the inner primary coating expands to a
greater extent than the outer primary coating during ribbon
stripping, at least in part due to the following reason. At
temperatures below the Tg of the polymeric coating, the polymers
present in the coating tend to act "glass-like", and therefore have
a low coefficient of expansion. However, at temperatures above the
Tg of the polymeric coating, the polymers tend to act "rubber-like"
and therefore have a higher coefficient of expansion than when
below the Tg of the polymeric coating. As the temperature of the
ribbon assembly is raised during ribbon stripping the polymer
present in the inner primary coating will usually be at a
temperature above their Tg and be more "rubber-like" well before
the polymers present in the outer primary coating reach their Tg.
Thus, as the applied stripping temperature is raised, the
"rubber-like" polymer present in the inner primary coating will
expand to a much greater extent, than the "glass-like" polymer in
the outer primary coating.
[0115] The Tg of the inner primary coating and that of the outer
primary coating usually cannot be matched because the outer primary
coating should have a higher Tg to provide the tough protective
properties required of the outer primary coating. In general, the
Tg of the outer primary coating is above 60.degree. C., whereas the
Tg of the inner primary coating is usually below 10.degree. C.,
preferably below about 0.degree. C., more preferably below about
-10.degree. C., and most preferably below about -20.degree. C.
[0116] However, it has been found that the relative expansion
characteristics of the inner and outer primary coatings can be
adjusted without substantially affecting the Tg of the coatings.
The expansion characteristics of the desired inner and outer
primary coatings should first be measured as follows. The change in
expansion from the ambient working temperature of the ribbon
assembly to the ribbon stripping temperature measured in one plane
"dL" is divided by an initial length of the one plane measured at
the ambient working temperature of the ribbon assemble "L",
hereinafter referred to as "(dL/L)". Ambient working temperatures
of ribbon assemblies are usually about 0.degree. C. to about
30.degree. C. It will be appreciated that for most coating
compositions the design ribbon stripping temperatures are usually
about 90.degree. C. to about 120.degree. C., but may be different
depending on the specific design parameters for the particular
coating composition.
[0117] The inner and/or outer primary coatings should be selected
or reformulated so as to maximize the (dL/L) of the outer primary
coating and while minimizing the (dL/L) of the inner primary
coating. Ideally, the (dL/L) of the outer primary coating should be
greater than that of the inner primary coating whereby the outer
primary coating will theoretically exert a normal force on the
inner primary coating in a direction away from the optical glass
fiber during ribbon stripping. However, such high (dL/L) values for
the outer primary coating in combination with retention of the
desired toughness properties of the outer primary coating are
usually unattainable. Nevertheless, increasing the (dL/L) of the
outer primary coating can significantly reduce the increase in
normal force on the inner primary coating during ribbon stripping
to provide a clean optical glass fiber which is substantially free
of residue.
[0118] FIG. 4 is a graph of the change in L ("dL") for a
commercially available outer primary coating as the temperature is
increased. In particular, for an L of 23.2 mm, the dL for a
temperature change from 25 C. (example of ambient temperature) to
100 C. (example of ribbon stripping temperature) can be calculated
as follows: 1 dL / L = ( delta L ) / L = ( 0.4 ) / 23.2 =
.01724
[0119] The dL/L value is independent of the length of the coating
selected for the measurement. Thus, for different L values, the
dL/L will be constant.
[0120] The normal force on the inner primary coating against the
optical glass fiber, which is caused by the differential in
expansion between the inner primary coating and outer primary
coating during ribbon stripping, can be calculated as follows. FIG.
5 illustrates a cross-sectional view of a glass optical fiber 7,
coated with an inner primary coating 8 and an outer primary coating
9. The outer primary coating 9 is the same as that in FIGS. 1 and
4. The radius of the outer surface of the inner primary coating at
25 C. is 95 microns, shown at 40. The radius of the inner surface
of the outer primary coating at 25 C. is 95 microns, also shown at
40. As the temperature of the ribbon assembly is increased to 100
C. during ribbon stripping, the inner primary coating and outer
primary coating expand.
[0121] The radius of the inner surface of the outer primary coating
at 100 C. is 96.379 microns, shown at 42. This value was calculated
as follows. The (dL/L) for the outer primary coating material
heated from 25 C. to 100 C. is 0.01724, as calculated from FIG. 4.
The radius of the inner surface of the outer primary coating at 25
C. (95 microns) is multiplied by (1+dL/L) for a temperature change
of 25 C. to 100 C. (1.01724) which provides a radius of the inner
surface of the outer primary coating at 100 C. of 96.638 microns.
However, this value must be corrected to take into account the
expansion in the thickness of the outer primary coating. The outer
primary coating has as thickness of 30 microns at 25 C. To obtain
the thickness at 100 C., the thickness at 25 C. (30 microns) is
multiplied by (1+dL/L) for a temperature change of 25 C. to 100 C.
(1.01724), which provides a thickness of 30.5172 microns. Thus, the
thickness of the outer primary coating expands 0.5172 microns when
heated from 25 C to 100 C. One half of this expansion occurs in the
direction of the inner primary coating. This assumes that the inner
primary coating will not substantially resist the expansion of the
outer primary. Thus, one half of 0.5172 must be subtracted from the
value obtained above for the radius of inner surface of the outer
primary coating at 100 C. (96.638 microns) to obtain a corrected
value of 96.379 microns. The change in radius over the temperature
change from 25 C. to 100 C. "dR" divided by the radius at 25 C. "R"
is then calculated to provide the value (dR/R).
[0122] The above measurements can be performed on the inner primary
coating selected to provide a value (dR/R) for the inner primary
coating. The radius of the inner primary coating at 100 C. is shown
at 44. The normal force on the inner primary coating against the
optical glass fiber, which is caused by the differential in
expansion between the inner primary coating and outer primary
coating during ribbon stripping is shown at 46.
[0123] The % expansion of the inner primary coating can be
calculated from the following:
((dR/R).sub.inner primary-(dR/R).sub.outer primary.times.100%
[0124] From a stress/strain curve, one skilled in the art can
easily use the % expansion to calculate the pressure of the inner
primary coating against the optical glass fiber, which is caused by
the differential in expansion between the inner and outer primary
coating during ribbon stripping. Multiplying the pressure by the
surface area of the inner primary coating against the optical glass
fiber provides the normal force of the inner primary coating
against the surface of the optical glass fiber.
[0125] Preferably, the (dR/R).sub.inner primary is decreased and/or
the (dR/R).sub.outer primary is increased to reduce the
differential in expansion between the inner and outer primary
coating during ribbon stripping, thereby reducing the normal force
of the inner primary coating against the surface of the optical
glass fiber.
[0126] Based on the above, it has been found that the normal force
can be decreased by reducing the pressure increase of. the inner
primary coating during ribbon stripping, by reformulating the inner
primary coating and/or outer primary coating to provide one or more
of the following properties:
[0127] (1) decreasing the elastic modulus (at ribbon stripping
temperature) of the outer primary coating so that it can stretch to
a greater extent to relieve more of the pressure build-up of the
inner primary coating during ribbon stripping,
[0128] (2) increasing the (dL/L) of the outer primary coating so
that the outer primary coating expands to a greater extent to allow
for more expansion of the inner primary coating during ribbon
stripping, and/or
[0129] (3) decreasing the (dL/L) of the inner primary coating to
reduce the pressure build-up of the inner primary coating.
[0130] The elastic modulus (at ribbon stripping temperature) of the
outer primary coating can be decreased by reducing the crosslink
density of the outer primary coating. The elastic modulus is
determined by the Elastic Modulus Test method, as discussed in the
DESCRIPTION OF TEST METHODS, below. Preferably, the elastic modulus
of the outer primary coating is adjusted to be between about 10 to
about 40 MPa, more preferably between about 10 to about 20 MPa, at
the ribbon stripping temperature. Outer primary coatings having an
elastic modulus in the range of between about 15 to about 40 MPa,
more preferably between about 30 and 40 MPa, have also been found
suitable as well as outer primary coatings having an elastic
modulus of greater than about 25 MPa. While it has been found that
the crosslink density of the outer primary coating can usually be
reduced without causing undesirable effects, the Tg of the outer
primary coating should remain high, to provide the outer primary
coating with the necessary toughness related properties to protect
the optical glass fiber. For example, to reduce the crosslink
density of the outer primary coating without reducing the Tg to
unacceptably low values, monofunctional monomers or oligomers,
which when cured exhibit a high Tg, can be used. Monofunctional is
understood herein as including monomers and oligomers having an
average of about 1 functional group capable of polymerization upon
exposure to actinic radiation. A high Tg is herein understood to be
at least about 40 C., preferably at least about 50 C.
[0131] Examples of suitable high Tg producing monofunctional
monomers and oligomers include, for example, isobornyl acrylate and
vinylcaprolactam. Such monomers can be utilized in amounts of about
1% to about 80%, preferably about 10 to about 50% by weight of the
total composition.
[0132] Very high Tg producing multifunctional monomers or
oligomers, such as tris-hydroxyethylisocyanurate triacrylate can
also be used in amounts up to about 30%, preferably up to about 20%
by weight, because they are effective at greatly increasing the Tg
of the outer primary coating without excessively increasing the
crosslink density.
[0133] The (dL/L) of the outer primary coating can be significantly
increased by incorporating a monomer or oligomer which when cured
exhibits a high(dL/L). For example, a suitable (dL/L), at the
desired ribbon stripping temperature, for the outer primary coating
has been found to be at least about 0.017, preferably at least
about 0.02, and most preferably at least about 0.023. These amounts
can be expressed as percentage increases in the length by
multiplying by 100. Therefore, the outer primary coating preferably
increases in length over the change in temperature from ambient
temperature to ribbon stripping temperature ("dL/L") of at least
about 1.7%, more preferably at least about 2%, and most preferably
at least about 2.3%. If the coefficient of friction of the inner
primary coating and/or the dL/L of the inner primary coating are
sufficiently low enough, the dL/L of the outer primary coating can
be less than 1.7% and still provide a fiber friction and normal
force that will result in a resistive force that is less than the
cohesive strength of the inner primary coating.
[0134] The high (dL/L) producing monomer or oligomer should be
added in an amount sufficient to provide a cured outer primary
coating with the desired level of (dL/L). For example, the high
(dL/L) monomer or oligomer can be added in an amount of about 10 to
about 70% by weight, more preferably about 10 to about 50% by
weight.
[0135] Examples of suitable high (dL/L) monomers or oligomers
include isobornyl acrylate, vinylcaprolactam, tricyclodecane
dimethanol diacrylate, and the adduct of 2 moles of
hydroxyethylacrylate and 1 mole of isophorone diisocyanate.
[0136] The (dL/L) of the inner primary coating can be decreased by
increasing the crosslink density of the inner primary coating.
However, when reformulating the inner primary coating to increase
the crosslink density, the Tg of the inner primary coating should
remain low to provide the optical glass fiber with adequate
protection from microbending. It has been found that the crosslink
density can be increased by using multifunctional monomers and
oligomers. Examples of suitable multifunctional monomers and
oligomers include, hexanedioldiacrylate, trimethyolpropane
triacrylate, and tripropyleneglycol diacrylate.
[0137] The ratio of the dL/L (inner primary) to the dL/L (outer
primary) at the desired ribbon stripping temperature should be low
enough to provide a fiber friction and normal force that results in
a resistive force between the inner primary coating and the optical
glass fiber that is less than the cohesive strength of the inner
primary coating. In general, the lower the ratio of dL/L (inner
primary) to dL/L (outer primary) the less the normal force that
will be applied to the inner primary coating against the surface of
the optical glass fiber. Thus, the ratio of the dL/L (inner
primary) to dL/L (outer primary) required to provide a fiber
friction force that results in a resistive force lower than the
cohesive strength of the inner primary coating will depend upon the
coefficient of friction of the inner primary coating. The lower the
coefficient of friction of the inner primary coating, the greater
the ratio of dL/L (inner primary) to dL/L (outer primary) that can
be tolerated and still provide a fiber friction and normal force
which results in a resistive force that is less than the cohesive
strength of the inner primary coating.
[0138] It has been found that a suitable ratio for the dL/L (inner
primary) to the dL/L (outer primary) at the desired ribbon
stripping temperature is less than about 2, preferably less than
about 1.7, and most preferably less than about 1.5.
[0139] The outer primary coating can also exert a force on the
inner primary, which is caused by shrinkage of the outer primary
coating during radiation curing of the outer primary coating. Thus,
to reduce this force oligomers and monomers can be selected to
provide a radiation-curable composition that exhibits reduced
shrinkage during radiation-curing.
[0140] If an ink coating is present, the ink coating can also exert
a normal force on the inner primary coating in a manner similar to
the normal force exerted by the outer primary coating. However, the
force exerted by the ink coating will. generally be significantly
less than the force exerted by the outer primary coating because
the ink coating is generally about an order of magnitude thinner
than the outer primary coating. The thickness of the ink layer is
usually only about 3 to about 8 microns.
[0141] If desired, the normal force exerted by the ink coating can
be adjusted in a similar manner as adjusting the normal force
exerted by the outer primary coating, because the ink coating in
general is also formed from monomers and oligomers similar to those
used to form the outer primary coating. In particular, the (dL/L)
of the ink coating can be adjusted to be closer to the (dL/L) of
the inner primary coating by reformulating the ink coating to
utilize monomers and/or oligomers that result in a coating having a
(dL/L) closer to the (dL/L) of the inner primary coating, as
described herein above in reference to the outer primary
coating.
[0142] The invention will be further explained by the following
non-limiting example.
COMPARATIVE EXAMPLES A-1 TO A-2
[0143] The compositions shown in Table 1 represent commercially
available coating compositions. Comparative Example A-1 is an
example of an outer primary coating and Comparative Example A-2 is
an example of an inner primary coating.
1 TABLE 1 Component Comp. Comp. (Amount in % by weight of total
Example Example composition) A-1 A-2 Oligomer
H-(T-PTMG650).sub.1.14-T-H 39 Oligomer H-(I-PTGL2000).sub.2-I-H
51.41 Bisphenol A Diglycidylether 29 Diacrylate Isobornyl Acrylate
10 6.86 Hexanediol Diacrylate 8.5 Phenoxyethyl Acrylate 10 Lauryl
Acrylate 5.95 Ethoxylated Nonylphenol Acrylate 20.91
Tripropyleneglycol Diacrylate 5.81 Vinyl Caprolactam 6.11
Diethylamine .1 Gamma Mercaptopropyl Trimethoxy 1 Silane
Thiodiethylene bis (3,5-di-tert- .5 .31 butyl-4-hydroxy)
hydrocinnamate 2,4,6-Trimethylbenzoyl diphenyl 2 1.54 phosphine
oxide 1-Hydroxycyclohexylphenyl Ketone 1 The oligomers were formed
by reacting the following components: H = Hydroxyethyl Acrylate T =
Toluene Diisocyanate I = Isophorone Diisocyanate PTGL2000 = 2000
molecular weight
polymethyltetrahydrofurfuryl/polytetrahydrofurfuryl copolymer diol
(Mitsui, NY) PTMG650 = 650 molecular weight
polytetramethyleneglycol diol (DuPont)
[0144] The compositions were suitably cured by exposure to UV light
from a Fusion D lamp. The dL/L for each coating was measured over
the temperature range of 25 C (ambient temperature) to 125 C
(highest usual stripping temperature).
[0145] For Comparative Example A-1, the dL/L for a temperature
change from ambient temperatures (25 C.) to ribbon stripping
temperatures (100 C.) was 1.42%.
[0146] For Comparative Example A-2, the dL/L for a temperature
change from ambient temperatures (25 C.) to ribbon stripping.
temperatures (100 C) was 2.3%.
[0147] Thus, the ratio of the dL/L (inner primary) to dL/L (outer
primary) was about 1.6, which would be acceptable if the
coefficient of friction of the inner primary coating was low
enough. However, the inner primary coating exhibited too high of a
coefficient of friction, because the fiber friction estimated by
using the fiber pull-out friction method described herein below was
too great. The fiber pull-out friction was 39 g/mm, which resulted
in a resistive force that was greater than the cohesive strength of
the inner primary coating. Therefore, substantial amounts of inner
primary coating residue were left on the optical glass fiber after
ribbon stripping using the above inner and outer primary
coatings.
[0148] Coefficient of Friction of Inner Primary Coating
[0149] From the above equations, fiber friction between the optical
glass fiber and inner primary coating can also be adjusted by
reducing the coefficient of friction of the inner primary coating
against the surface of the optical glass fiber. By reducing the
coefficient of friction of the inner primary coating, the
"rubber-like" drag of the inner primary coating on the optical
glass fiber is reduced.
[0150] Preferably, the coefficient of friction of the inner primary
coating is reduced without reducing the adhesion of the inner
primary coating to the surface of the optical glass fiber. If the
adhesion is reduced, then undesirable delamination of inner primary
coating from the surface of the optical glass fiber can occur.
[0151] It has been found that the fiber friction can be adequately
adjusted to a value which provides resistive force below the
cohesive strength of the inner primary coating by adjusting the
coefficient of friction of the inner primary coating with the use
of one or more of the novel slip additives described herein.
Surprisingly, the coefficient of friction can be reduced to such a
level without substantially reducing the adhesion of the inner
primary coating to the optical glass fiber as follows.
[0152] Preferably, the ratio of the dL/L (inner primary) to the
dL/L (outer primary) is adjusted in combination with adjusting the
coefficient of friction of the inner primary coating to provide a
fiber friction value which results in a resistive force that is
less than the cohesive strength of the inner primary coating.
[0153] In practice, ribbon assemblies are generally stripped using
a heated stripping tool. However, using the inventive concepts
described herein, the present invention includes ribbon assemblies
which surprisingly can be ribbon stripped at much lower
temperatures, such as ambient temperatures, to provide bare optical
glass fibers which are substantially free of residue. It has been
found that if the fiber friction between the inner primary coating
and the surface of the optical glass fiber and/or the normal force
is adjusted to a level which provides a resistive force lower than
the cohesive strength of inner primary coating, the ribbon assembly
will be ribbon strippable. Therefore, if a ribbon assembly which is
adapted to provide ribbon strippability at ambient temperatures is
desired, the fiber friction can be adjusted to a level to provide a
resistive force that is less than the cohesive strength of the
inner primary coating using slip agents as discussed herein.
Alternatively, if the ribbon assembly is adapted to provide ribbon
strippability at temperatures greater than ambient temperatures,
the resistive force can be adjusted to a level lower than the
cohesive strength of the inner primary coating by adjusting the
ratio of the dL/L (inner primary) to the dL/L (outer primary) to
provide a lower normal force and fiber friction, and/or adjusting
the coefficient of friction of the inner primary coating using slip
agents to provide a lower fiber friction.
[0154] Novel Radiation-Curable, Silicone-Silane Oligomer
[0155] This invention also provides a novel type of
radiation-curable oligomer that can be used to adjust the fiber
friction between the inner primary coating and the surface of the
optical glass fiber. The radiation-curable oligomer comprises a
glass coupling moiety, a slip agent moiety, and a radiation curable
moiety, each moiety being linked to a single composite oligomer
molecule through covalent bonding to provide a composite oligomer.
Such linkage of all three moieties is heretofore unknown. Linkage
of these moieties can be direct so that no intermediate linking
group between the oligomer and the moiety is required.
Alternatively, however, the linkage can be indirect by using
intermediate linking groups.
[0156] A variety of glass coupling, slip agent, and radiation
curable moieties are known in the art. The present invention can be
practiced with use of various embodiments using different
combinations of these moieties to produce a composite oligomer. A
person skilled in the art will easily be able to prepare
combinations of these various moieties from the present disclosure
and general knowledge in the art.
[0157] Radiation-curing can occur by reaction of the composite
oligomer's radiation-curable moieties with themselves or with
radiation-curable moieties bound to other components of a
formulation. In general, curing of the composite oligomer occurs in
concert with other radiation-curable components. Radiation-curing,
in the present invention, is associated with reaction of the
radiation-curable moiety, not with the glass coupling or slip agent
moieties. For example, although the glass coupling moiety will be
reactive, and is often sensitive to hydrolysis and condensation
reactions, these types of reactions are not the principal cure
mechanism.
[0158] The molecular weight of the oligomer is not limited. In
general, however, the molecular weight of the oligomer in its
uncured state is usually between about 200 and about 10,000,
preferably between about 500 and about 5,000. Molecular weight as
used throughout this disclosure generally means number average
molecular weight when measured, or the theoretical calculated
molecular weight based on the reactants and reaction conditions
used to make the composite oligomer.
[0159] There is no particular limitation on the molecular
architecture of the composite oligomer, although in general, linear
or substantially linear oligomeric structures are used rather than
non-linear, cyclic, or branched structures. To the extent that the
inventive concept can be practiced, however, branched or other
non-linear structures are also envisioned and are not excluded. A
substantially linear structure means that there is a single,
dominant linear oligomeric backbone which is "capped" at the two
ends of the backbone. The amount of branching units in the backbone
is generally less than about 10 mole %, and preferably, less than
about 5 mole %. The linear backbone may contain one or more types
of repeat units, although preferably, one major type of repeat unit
is used. Nevertheless, block or random copolymeric structures can
be used if necessary. With a substantially linear backbone, the
number of branch points in the backbone will be kept to a minimum,
and preferably, will not be used. Synthetic simplicity in the
oligomer structure is preferred to the extent that cost-performance
can be achieved.
[0160] The term "glass coupling moiety" can be readily understood
by a person skilled in the art and is understood to mean a
functional group which is known or has the ability to improve
adhesion to an inorganic surface or at an inorganic-organic
interface, and in particular, a glass surface or at a glass-polymer
interface. Such glass coupling moieties are associated with
conventional coupling agents or adhesion promoters, as known to
those skilled in the art. These conventional coupling agents
generally have (1) an organic functional group which bonds with, or
is at least associated with, the organic material at the interface,
and (2) an inorganic component which bonds, usually covalently, to
the inorganic material at the interface. Although the complexities
of such bonding are not fully understood, usually, bonding to the
inorganic surface occurs following hydrolysis and/or condensation
reactions.
[0161] Exemplary conventional silane coupling agents are disclosed
in E. P. Plueddemann's Silane Coupling Agents, Plenum Press (1982),
the complete disclosure of which is hereby incorporated by
reference. Non-silane types of coupling agents are also known and
include, for example, chromium, orthosilicate, inorganic ester,
titanium, and zirconium systems. Although the present invention is
preferably practiced with use of silane glass coupling moieties,
the invention is not so restricted, and a person skilled in the art
is enabled by the present disclosure to use these other systems as
well.
[0162] In the present invention, the glass coupling moieties are
not part of a conventional coupling agent, but are incorporated
covalently into the oligomer in a manner which preserves their
coupling function to the inorganic surface or at the
inorganic-organic interface. In a preferred embodiment, for
example, the organic component of a conventional coupling agent is
linked covalently, either directly or indirectly, with the
composite oligomer together with the slip agent and radiation
curable moieties. After this linkage, the glass coupling moiety
will still have its inorganic component effective for bonding with
the inorganic surface or at the inorganic-organic interface.
However, the invention is not so limited, and the glass coupling
moiety is not necessarily linked to the composite oligomer by
reaction of the organic functional group of a conventional coupling
agent.
[0163] Silane coupling moieties are preferred. These moieties can
be created by covalently linking a conventional coupling agent or
adhesion promoter with the oligomer. Representative types of silane
coupling moieties have been disclosed in the aforementioned
Plueddemann reference and the product information publication from
Union Carbide entitled "UNION CARBIDE.RTM. Organofunctional Silanes
Products and Applications" (1991, 1992), the complete disclosure of
which is hereby incorporated by reference. The inorganic component
of the conventional silane coupling agent is generally represented
by the formula:
--Si(OR).sub.3
[0164] where R is a conventional lower, and preferably, a
C.sub.1-C.sub.4, alkyl group such as methyl or ethyl which imparts
at least some hydrolyzability to the silane. Other types of R
groups are also known in the art, however, and the invention is not
particularly limited by the particular R group or silane structure
to the extent that glass coupling can occur. Generally, at least
one hydrolyzable "--Si--O--R" linkage will be present in the glass
coupling moiety to facilitate coupling to the surface of the
optical glass fiber. Preferably, there is more than one such
linkage. Hydrolyzable means that this linkage is sensitive to
reaction with water to generate "--Si--OH" linkages. In turn,
"--Si--OH" linkages are believed to condense to form
"--Si--O--Si--" linkages. In many cases, hydrolysis may even begin
to occur with exposure to atmospheric moisture. Hydrolysis of
silanes and glass surfaces in the context of optical fiber coatings
is discussed in, for example: (i) the chapter entitled "Coating and
Jackets", Chapter 10, Blyler et al. Optical Fiber
Telecommunications, 1979, pgs. 299-341, and (ii) S. Wu, Polymer
Interface and Adhesion, Marcel Dekker, 1982, pgs. 406-434, the
complete disclosures of which are hereby incorporated by
reference.
[0165] Common organic functionalities of the silane coupling agents
include, for example, amino, epoxy, vinyl, methacryloxy,
isocyanato, mercapto, polysulfide, and ureido. Using synthetic
methods known in the art, the organic functionality can be reacted
with the oligomer to yield a covalent linkage between the glass
coupling moiety and the oligomer. In a preferred embodiment, for
example, mercaptopropyl silane is linked with an oligomer
containing an isocyanate group to form a thiourethane adduct
between the mercapto group and the isocyanate group. Although a
strong linkage is preferred, the present invention encompasses the
possibility that although a covalent linkage is formed, the
covalent linkage may not be strong and may, for example, be
sensitive to disruption with the application of heat. However, as
long as the glass coupling moiety produces the desirable effect of
promoting adhesion, the covalent linkage is sufficient. If
necessary, catalysts may be used to promote linkage formation.
[0166] Slip agents when used to practice this invention do not
substantially affect the adhesion of the inner primary coating to
the surface of the optical glass fiber. Instead, the slip agents
reduce the sliding force of the inner primary coating against the
surface of the optical glass fiber, once the bonds between the
surface of the optical glass fiber and inner primary coating are
broken (i.e. after the inner primary coating has been
delaminated).
[0167] Slip agents are also known in the art as, among other
things, release, antiblocking, antistick, and parting agents. Slip
agents are commonly oligomeric or polymeric and are usually
hydrophobic in nature, with the most common examples including
silicones (or polysiloxanes), fluoropolymers, and polyolefins. If
desired, the slip agent moiety can include silicones,
fluoropolymers, and/or polyolefins in combination with polyesters,
polyethers and polycarbonates. Slip agents are disclosed in, for
example, the article entitled "Release Agents" published in the
Encyclopedia of Polymer Science, 2nd Ed., Vol. 14,
Wiley-Interscience, 1988, pgs. 411-421, the complete disclosure of
which is hereby incorporated by reference. Although slip agents
operate over a wide variety of interfaces, the present invention is
particularly concerned with an interface of a glass surface, and in
particular, a glass-organic coating interface between the inner
primary coating and the surface of the optical glass fiber. A slip
agent can be covalently incorporated into the composite oligomer as
a slip agent moiety.
[0168] In a preferred embodiment, the slip agent moiety is the
principal component of the oligomer in terms of weight percent
because the slip agent moiety itself is usually oligomeric in
nature, and the glass coupling and radiation-curable moieties are
usually of lower molecular weight. For example, the slip moiety can
be up to about 95 wt. % of the total composite oligomer weight when
the three moieties are directly linked together. However, when an
oligomeric backbone is present, the slip agent usually can be up to
about 85 wt. % of the composite oligomer weight. As with the
molecular weight of the composite oligomer of the present
invention, the molecular weight of the slip agent moiety is not
strictly limited, but will generally be between about 150 and about
9,500, preferably, between about 400 and about 4500.
[0169] As with the molecular architecture of the oligomer, there is
no particular limitation on the molecular architecture of the slip
agent moiety, although in general, substantially linear structures
can be used. Non-linear or branched structures, however, are not
excluded. Oligomeric slip agent moieties, when present, may contain
different kinds of repeat units, although preferably, there is one
main type of repeat unit.
[0170] Oligomeric silicone slip agent moieties are preferred, and
oligomeric silicones comprising substantial portions of methyl side
groups are particularly preferred. The side groups preferably
impart hydrophobic character to the silicone. Other preferred side
groups include ethyl, propyl, phenyl, ethoxy, or propoxy. In
particular, dimethylsiloxane repeat units represented by the
formula, "--OSi(CH.sub.3).sub.2--" are preferred.
[0171] In a preferred embodiment, the end groups on a substantially
linear silicone oligomer can be linked with a radiation curable
moiety at one end and a slip agent moiety at the other end. Such
linkage can involve intermediate linkage groups. Although linkage
at the silicone oligomer end group is preferred, the silicone
moiety can be tailored for linkage with slip agent and
radiation-curable moieties at other points in the oligomer molecule
besides the end groups. For example, functional groups can be
incorporated throughout the molecular structure of the silicone
oligomer that are linked with the radiation-curable and slip agent
moieties. Examples of functionalized silicones which can be
incorporated into the oligomer include polyether, polyester,
urethane, amino, and hydroxyl.
[0172] Other types of slip agent moieties including those made from
fluorinated slip agents can also be used. Examples of suitable
fluorinated slip agents include FC-430, FX-13, and FX-189
(Minnesota Mining and Manufacturing), Fluorolink E (Ausimont), and
EM-6 (Elf Atochem).
[0173] Generally, the composite oligomer of the present invention
is surface active because of the glass coupling moieties, and in
particular, may tend to concentrate at coating interfaces, such as
the glass-coating interface, if not bound in the inner primary
coating. However, the covalent binding of the composite oligomer
after cure, due to the radiation-curable moiety, may retard such
surface activity or migration. Surface activity means that the
composite oligomer, when placed in a formulation, tends to migrate
to the surface of the formulation rather than be dispersed evenly
throughout the formulation.
[0174] The radiation-curable moiety should help ensure that the
composite oligomer is covalently linked within a radiation-curable
coating so that the composite oligomer cannot be extracted or
volatilized from the cured coating without breaking covalent
bonds.
[0175] The radiation-curable moiety can include any functional
group capable of polymerizing under the influence of, for example,
ultraviolet or electron-beam radiation. One type of
radiation-curable functionality is, for example, an ethylenic
unsaturation, which in general is polymerized through radical
polymerization, but can also be polymerized through cationic
polymerization. Examples of suitable ethylenic unsaturation are
groups containing acrylate, methacrylate, styrene, vinylether,
vinyl ester, N-substituted acrylamide, N-vinyl amide, maleate
esters and fumarate esters. Preferably, the ethylenic unsaturation
is provided by a group containing acrylate, methacrylate or styrene
functionality. Most preferably, the ethylenic unsaturation is
provided by a group containing acrylate functionality.
[0176] Another type of functionality generally used is provided by,
for example, epoxy groups, or thiol-ene or amine-ene systems. Epoxy
groups, in general, can be polymerized through cationic
polymerization, whereas the thiol-ene and amine-ene systems are
usually polymerized through radical polymerization. The epoxy
groups can be, for example, homopolymerized. In the thiol-ene and
amine-ene systems, for example, polymerization can occur between a
group containing allylic unsaturation and a group containing a
tertiary amine or thiol.
[0177] The amount or number of glass coupling, slip agent, and
radiation curable moieties in the composite oligomer is not
particularly limited provided that advantages of the present
invention can be achieved and the inventive concept is practiced.
Thus, a single molecule of the composite oligomer can contain
multiple numbers of glass coupling, slip agent, or
radiation-curable moieties, although in a preferred embodiment, a
single oligomeric molecule contains one glass coupling, one slip
agent, and one radiation-curable moiety.
[0178] The glass coupling, slip agent, and radiation curable
moieties should be covalently linked together in the oligomer.
There is no particular limitation to how this linkage is effected
provided that advantages of the present invention are achieved and
the inventive concept practiced. Linkage may entail direct linkage
to the oligomer, or alternatively, indirect linkage to the
oligomer. Intermediate linking groups will generally operate by way
of two functional groups on a linking compound which can link, for
example, the radiation-curable moiety with the slip agent moiety,
or link the glass coupling moiety with the slip agent moiety.
[0179] Representative linking compounds include diisocyanate
compounds, wherein linkage occurs by formation of urethane,
thiourethane, or urea links by reaction of hydroxyl, thiol, and
amino groups respectively, with isocyanate. Such diisocyanate
compounds are well-known in the polyurethane and radiation curable
coating arts. Aromatic or aliphatic diisocyanates can be used,
although aliphatic diisocyanates are preferred. Other linkages can
be through, for example, carbonate, ether and ester groups.
Preferably, urethane, urea or thiourethane groups are used as the
linking groups.
[0180] The oligomer, therefore, preferably comprises within its
structure at least one linkage represented by
--NH--CO--X--
[0181] wherein X is an oxygen, sulfur, or nitrogen atom. Urethane
and thiourethane groups are most preferred. Urethane groups, for
example, can hydrogen bond.
[0182] Although the present invention is not limited to one
particular molecular architecture for the composite oligomer, in a
preferred embodiment which makes use of intermediate linking
groups, the composite oligomer can be represented by the following
generic structure:
R-L.sub.1-A-L.sub.2-C
[0183] wherein A represents the slip agent moiety,
[0184] R represents a radiation-curable moiety,
[0185] C represents the glass coupling moiety, and
[0186] L.sub.1 and L.sub.2 represent linking groups.
[0187] L.sub.1 and L.sub.2 can be independently any group capable
of providing a covalent link between the "R" moiety and the "A"
moiety or between the "C" moiety and the "A" moiety. Based on the
disclosure provided herein, one skilled in the art will easily be
able to understand what linking groups are suitable for the
particular "A", "C" and "R" groups selected.
[0188] In particular, urethane and thiourethane groups are
preferred. Urethane and thiourethane linking groups are formed by,
for example, (i) linking a hydroxyl end-capped oligomer with a low
molecular weight diisocyanate compound at both oligomer ends
without extensive coupling of the oligomer, (ii) linking the
isocyanate end-capped oligomer with a low molecular weight
hydroxyacrylate compound, or (iii) linking the isocyanate
end-capped oligomer with a low molecular weight mercapto
compound.
[0189] The linking groups, however, are considered optional. In
other words, the oligomer also can be represented by the following
generic structures:
R-L.sub.1-A-C,
R-A-L.sub.2-C, or
R-A-C.
[0190] Although the present invention is disclosed in terms of the
aforementioned groups or moieties, other groups can in principle be
incorporated into the molecular structure to the extent that the
advantages of the present invention can be achieved and the
inventive concept practiced.
[0191] A preferred embodiment of the present invention is the
preparation of a composite oligomer with use of the following
ingredients: a silicone oligomer having two hydroxyl end groups
(slip agent moiety), isophorone diisocyanate (linkage),
hydroxyethyl acrylate (radiation-curable moiety), and
mercaptopropyl silane (glass coupling moiety), isophorone
diisocyanate (IPDI) serves to end-cap both ends of the silicone
diol oligomer and provide a linking site with the hydroxyethyl
acrylate at one end of the silicone oligomer and with the
mercaptopropyl silane at the other end.
[0192] A preferred application for the composite oligomer is as an
oligomeric additive, or even as a main oligomeric component, in a
radiation-curable coating, and in particular, an inner primary,
optical glass fiber coating. The amount of oligomeric additive
incorporated into the radiation curable matrix is not particularly
limited but will be sufficient or effective to achieve the specific
performance objectives of the particular application. In general,
however, a suitable amount will be between about 0.5 wt. % and
about 90 wt. %, preferably, between about 0.5 wt. % and about 60
wt. %, and more preferably, between about 0.5 wt. % and about 30
wt. % with respect to the total weight of the radiation-curable
coating formulation. In general, higher molecular weight composite
oligomers will be present in a radiation-curable coating in greater
weight percentages than lower molecular weight composite
oligomers.
[0193] The composite oligomer functions to tailor the properties of
formulations which exhibit too great a coefficient of friction or
too low adhesion. Specifically, the composite oligomer can increase
the adhesion if the adhesion is unacceptably low, and in particular
unacceptably low in the presence of moisture. Alternatively, the
composite oligomer can reduce the coefficient of friction of a
coating. Conventional coupling additives and slip agents cannot
perform this dual function.
[0194] If desired, although a reduction in the number of additives
is desirable, the composite oligomer can be used in conjunction
with conventional coupling and slip agents to improve absolute
performance or cost-performance. In a preferred embodiment, for
example, the composite oligomeric can be used in conjunction with a
functional organosilane compound such as, for example,
mercaptopropyl silane. For example, a hydroxybutylvinylether adduct
with OCN--(CH.sub.2).sub.3Si(OCH.sub.3).sub- .3 can also be used
together with the composite oligomer.
[0195] The composite oligomer can be incorporated into a wide
variety of radiation-curable formulations. There are no particular
limitations provided that the inventive concept is practiced and
advantages accrue. One skilled in the art of formulating
radiation-curable coatings will easily be able to incorporate the
composite oligomer therein to provide the desired properties.
[0196] In optical glass fiber coating applications, for example,
other formulation components generally include:
[0197] (i) at least one multi-functional radiation-curable
oligomer, which is a different oligomer than the composite oligomer
of the present invention, to provide a cross-linked coating;
[0198] (ii) at least one reactive diluent to adjust the viscosity
to a level acceptable for application to optical glass-fibers,
and
[0199] (iii) at least one photoinitiator.
[0200] Additives such as antioxidants, and as already noted,
coupling and slip agents may also be utilized.
[0201] Radiation-curing is generally rapidly effected with use of
ultraviolet light, although the present invention is not so
limited, and a person of skill in the art can determine the best
cure method. Radiation-curing results in polymerization of at least
some of the radiation-curable moieties present in the composite
oligomer which covalently links the composite oligomer to itself
or, more preferably, other radiation-curable components in the
formulation. The chemical processes which occur upon mixing and
curing formulations are in some cases complex and may not be fully
understood. The present invention, however, is not limited by
theory and can be readily understood and practiced by persons of
skill in the art. The formulations of the present invention, just
like the composite oligomer, can be in pre-cured, partially cured,
and in cured states. The term component, which defines additives
and compounds used to prepare the formulations, generally refers to
starting materials before mixing. After mixing, interactions or
even reactions between the components may occur.
[0202] The composite oligomer can be incorporated into inner
primary-coating compositions, outer primary coating compositions,
ink compositions and matrix forming compositions. The composite
oligomer also can be incorporated into so-called single coating
systems.
[0203] In general, the coating substrate will be an inorganic or
glass substrate, although in principle, other substrates such as
polymeric substrates may also be effectively used. The substrate
preferably has the capacity to couple with the glass coupling
moiety of the oligomeric additive. In a preferred application, the
coating substrate is an optical glass fiber, and in particular, a
freshly drawn, pristine optical glass fiber. Freshly prepared
optical glass fiber is known in the art to be responsive to glass
coupling agents. Exemplary methods of coating optical fibers are
disclosed in, for example, U.S. Pat. Nos. 4,474,830 and 4,913,859,
the complete disclosures of which are hereby incorporated by
reference.
[0204] The present inventions will be further explained by use of
the following non-limiting examples.
EXAMPLE 2-1 AND COMPARATIVE EXAMPLES B-1 AND B-2
[0205] Synthesis of Novel Composite Oligomer
[0206] A 1,000 mL four-necked flask was charged with isophorone
diisocyanate (55.58 g). 2,6-di-tertbutyl-4-methylphenol (0.12 g)
and dibutyltin dilaurate (0.24 g) were added to the flask. 14.51
grams of Hydroxyethyl acrylate was added over a 90 minute period
while maintaining the temperature below 40 C. At the end of 90
minutes, the temperature was increased to 40 C., and the mixture
was stirred at 40 C. for one hour. The temperature was allowed to
decrease to about 30 C. Mercaptopropyl silane (28.13 g of an 87.1%
pure product) was added over 90 minutes during which time the
temperature was maintained below 40 C. After the addition of
mercaptopropyl silane, the temperature was increased to 40 C., and
the reaction mixture was stirred at 40 C. for 17-18 hours. 300 g of
a 50% ethoxylated polydimethylsiloxane diol of 1200 equivalent
weight Q4-3667 (Dow Corning) was then added, and the temperature
was increased to 70 C. After about six hours, the isocyanate
content was measured to be about zero percent. The temperature was
decreased to 50 C. Based on the reaction conditions and reactants,
a composite silicone silane acrylate oligomer was formed having the
following structure:
H-I-(Q4-3667)-I-M
[0207] wherein: H=hydroxyethylacrylate,
[0208] I=isophorone diisocyanate,
[0209] Q4-3667=the above described silicone diol, and
[0210] M=mercaptopropyl silane
[0211] Preparation of Pre-Cured Formulation
[0212] The components shown in Table 2 were combined, except for.
the composite oligomer and the silane coupling agent. The
components were heated to about 60 C. and mixed to form homogeneous
mixtures. The composite oligomer and silicone coupling agent were
mixed therein and the mixture was heated for approximately 15
minutes at 60 C. to form an improved radiation-curable, inner
primary, optical glass fiber coating composition, Example 2-1. The
mixtures for Comparative Examples B-1 and B-2 were prepared
similarly. Drawdowns of the compositions were made and then
suitably cured by exposure to UV light to form cured coatings. The
cured coatings were tested for resistance to delamination and fiber
pull-out residue using the following methods.
[0213] Water Soak Delamination Test
[0214] A drawdown of each inner primary coating composition was
made to form a 75 micron film of the inner primary coating
composition on microscope slides and then cured by exposure to 1.0
J/sq cm, from a Fusion D lamp, 120 W/cm, under a nitrogen
atmosphere. Then, a drawdown of each outer primary coating was made
to form a 75 micron film of the outer primary coating composition
over the cured 75 micron inner primary film, and then cured in the
same manner as the inner primary coating.
[0215] Deionized water was placed in a 500 ml beaker and the coated
microscope slides were soaked in the water. The beaker containing
the coated slides was then placed in a 60 C. hot water bath. The
films were observed for delamination periodically. The time when
the first signs of delamination appeared were recorded.
[0216] Fiber Pull-Out Residue Test
[0217] The operation of stripping coatings from optical fibers to
leave a bare glass surface was simulated by pulling four bare glass
fibers out of a layer of cured inner primary coating. Microscopic
examination of the pulled-out fibers at low magnification (e.g.,
10.times.) clearly revealed the presence or absence of debris on
the glass surface. If debris was present, the amount of debris was
noted. The results of these tests are provided in Table 2.
2 TABLE 2 Component (Amount is % by weight based on total weight
Comp. Ex Comp. Ex of composition) Ex. 2-1 B-1 B-2 Urethane acrylate
53.2 56 53.87 oligomer Isodecyl Acrylate 13.3 14 13.47
Ethoxylated-nonylphenol 24.22 25.5 24.53 Monoacrylate Silicone
Silane 5 0 0 Oligomer H-I-Q4-3667-I-A189 Q4-3667 (Dow Corning) 0 0
3.8 Photoinitiator 2.85 3 2.89 Antioxidant 0.47 0.5 0.48
y-Mercapto-propyl 0.95 1.0 0.96 Trimethoxy-Silane Fiber no lot of
no Pull-out Residue Test residue residue residue Delamination, none
none delam. if any, after After 1 the hot water hour at soak* 60 C.
The oligomers were formed by reacting the following monomers: H =
Hydroxyethyl Acrylate I = Isophorone Diisocyanate Q4-3667 =
ethoxylated polydimethylsiloxane diol, MW of 1200 (Dow Corning)
*Samples were aged for 4 hours at 60 C.. Then the water bath was
shut-off for about 70 hours. The temperature was then brought back
to 60 C. for an additional 48 hours.
[0218] Comparative Example B-1 was a formulation which did not
contain the composite oligomer of the present invention, but which
contained a silane coupling agent. However, poor results were
obtained in the pull-out test because adhesion was too strong.
[0219] Comparative Example B-2 was a formulation which contained a
conventional silicone slip agent. The silicone slip agent improved
the results of the pull-out test compared to Comparative Example A,
but only at the expense of hydrolytic interfacial adhesion.
[0220] Example 2-1 was a formulation that contained the composite
oligomer of the present invention. The composite oligomer
remarkably improved the results of the pull-out test but not at the
expense of hydrolytic interfacial adhesion.
EXAMPLES 2-2 AND 2-3 AND COMPARATIVE EXAMPLES B-3 and B-4
[0221] These Examples and Comparative Examples were conducted to
demonstrate the effect of the composite oligomer on glass plate
adhesion. The formulations shown in Table 3 were prepared in the
same manner as in Example 2-1 and Comparative Examples B-1 and B-2.
The silicone silane acrylate oligomer was prepared in the same
manner as in Example 2-1, except that a silicone diol HSi-2111
(Tego Chemie) was used instead of Q4-3667 (Dow Corning).
[0222] Films of the coating materials (75 microns thick) were
prepared on microscope slides and then cured by exposure to UV
light. A commercially available outer primary coating was formed on
top of the coatings. The films were soaked in water at 60 C. and
then examined for delamination. In addition, dry and wet adhesion
was measured at 50% and 95% relative humidity (RH), respectively.
The results are summarized in Table 3.
[0223] Dry (50% RH) and wet (95% RH) adhesion can be measured by
recognized test methods. For example, as explained in U.S. Pat. No.
5,336,563 (Coady et al.) and U.S. Pat. No. 5,384,342 (Szum), the
wet and dry adhesion was tested on cured film samples prepared by
drawing down, with a Bird Bar, a 75 micron film of the coating
compositions on glass microscope slides and cured by exposure to
1.0 J/sq cm, from a Fusion D lamp, 120.W/cm, under a nitrogen
atmosphere, as noted above in Example 2-1.
[0224] The samples were then conditioned at a temperature of
23.+-.2.degree. C. and a relative humidity of 50.+-.5% for a time
period of 7 days. A portion of the film was utilized to test dry
adhesion. Subsequent to dry adhesion testing, the remainder of the
film to be tested for wet adhesion was further conditioned at a
temperature of 23.+-.2.degree. C. and a relative humidity of 95%
for a time period of 24 hours. A layer of polyethylene wax/water
slurry was applied to the surface of the further conditioned film
to retain moisture.
[0225] The adhesion test was performed utilizing apparatus which
included a universal testing instrument, e.g., an Instron Model
4201 commercially available from Instron Corp., Canton, Mass., and
a device, including a horizontal support and a pulley, positioned
in the testing instrument.
[0226] After conditioning, the samples that appeared to be uniform
and free of defects were cut in the direction of the draw down.
Each sample was 6 inches long and 1 inch wide and free of tears or
nicks. The first one inch of each sample was peeled back from the
glass. The glass was secured to the horizontal support with the
affixed end of the specimen adjacent the pulley. A wire was
attached to the peeled-back end of the sample, run along the
specimen and then run through the pulley in a direction
perpendicular to the specimen. The free end of the wire was clamped
in the upper jaw of the testing instrument which was then
activated. The test was continued until the average force value, in
grams force/inch, became relatively constant. The preferred value
for wet adhesion is at least about 5 g/in.
3TABLE 3 Component (Amount is parts Comp. Ex. Comp. Ex. by weight)
Ex. 2-2 Ex. 2-3 B-3 B-4 Oligomer C 49.22 49.22 49.22 49.22 H-I-
(PTHF2000-I).sub.2-H Ethoxylated 24.76 24.76 24.76 24.76
nonylphenol Acrylate Lauryl Acrylate 16.64 16.64 16.64 16.64 2,4,6-
3.0 3.0 3.0 3.0 trimethylbenzoyl- Diphenyl Phosphine Oxide
Thiodiethylene 0.46 0.46 0.46 0.46 bis (3,5-di-Tert- Butyl-4-
Hydroxy) hydrocinn amate gamma- 0.92 -- 0.92 Mercaptopropyl
Trimethoxy Silane Silicone Silane 5 5 -- -- Acrylate Oligomer
H-I-HSi2111-I-M Adhesion at 50% 45 14 27 9 RH (g/in) Adhesion at
95% 34 12 20 4 RH (g/in) 60 C. Water Soak No Slight No Delami-
Delami- Delami- Delami- nation After nation nation naion After 8 15
After After Hours; Minutes 24 15 Slight Hours Minutes Delami-
nation After 24 Hours The oligomers were formed by reacting the
following monomers: H = Hydroxyethyl Acrylate I = Isophorone
Diisocyanate M = Mercapto Silane PTHF2000 = 2000 molecular weight
Polytetramethylene Ether Glycol (BASF) HSi2111 = a silicone diol
having a MW of 1000 (Tego Chemie)
[0227] The results in Table 3 indicate that the composite oligomer
is not only able to improve adhesion to the glass surface, but is
also able to act synergistically with a conventional silane
coupling agent.
EXAMPLE 2-4
[0228] The formulation shown in Table 4 was prepared in the same
manner as in Example 2-1. The silicone silane acrylate oligomer was
the same as that prepared in Example 2-1.
[0229] A film of the coating material (75 micron thick) was
prepared on glass plates and then cured by exposure to UV light in
the same manner as above. The tensile strength, elongation and
modulus were measured.
[0230] A 75 micron film of the coating material was also prepared
and suitably cured. The crack propagation was then measured. A
fiber pull-out friction test was also conducted, as described
herein. The predicted ribbon strip cleanliness was calculated. The
results are shown in Table 4.
4 TABLE 4 Component Example (Amount in % by weight of total
composition) 2-4 H-I-(PTGL2000-I).sub.2-H 49.24 Ethoxylated
Nonylphenol Acrylate Ester 25.46 Diphenyl (2,4,6-trimethylbenzoyl)
Diphenyl 3 Phosphine Oxide and 2-Hydoxy-2-Methyl-1-
Phenyl-1-Propanone blend Lauryl Acrylate 16 Thiodiethylene bis
(3,5-di-Tert-Butyl-4- 0.5 Hydroxy) hydrocinnamate H-I-HSi2111-I-M 5
Mercaptopropyl trimethoxy silane 0.8 Test Results Viscosity, mPa
.multidot. s at 25 C. 7000 Tensile Strength, MPa 0.8 Elongation, %
230 Modulus, MPa 1 Dose@95% Modulus, J/cm.sup.2 0.64 E' = 1000 MPa,
.degree. C. -66 E' = 100 MPa, .degree. C. -50 Peak TAN Delta
.degree. C. -40 E.sub.0, MPa 1.3 Strip Cleanliness Predicted 3
Crack Propagation, mm 1.49 Fiber Pull-out Friction, g/mm 18.5 The
oligomers were formed by reacting the following components: H =
Hydroxyethyl Acrylate I = Isophorone Diisocyanate M =
Mercaptopropyl trimethoxy silane PTGL2000 = 2000 molecular weight
polymethyltetrahydrofurf- uryl/polytetrahydrofurfuryl copolymer
diol (Mitsui, NY) HSi2111 = a silicone diol having a MW of 1000
(Tego Chemie, or Gold Schmidt Chemical Corp.)
[0231] From the above test data, surprisingly, the novel silicon
silane acrylate oligomer can be used to provide an inner primary
coating having a fiber friction that provides a resistive force
that is less than the cohesive strength of the inner primary
coating. This finding is based on the predicted strip cleanliness
being about 3. A value of about 3 or less is very good and will
usually provide a bare optical glass fiber which is suitable for
connection to another optical glass fiber or component of a light
transmission assembly, without having to wipe residue from the bare
optical glass fiber.
[0232] Description of Test Methods Used Herein
[0233] Predicted Strip Cleanliness Test Method
[0234] The predicted strip cleanliness is the predicted degree of
cleanliness of a bare optical glass fiber after the inner primary
coating has been removed during ribbon stripping. A lower number is
better.
[0235] Surprisingly, it has been found that the degree of
cleanliness of a bare optical glass fiber of a selected ribbon
assembly can be predicted by measuring the following two properties
of the inner primary coating:
[0236] (1) fiber pull-out friction; and
[0237] (2) crack propagation.
[0238] The crack propagation is a measure of the cohesive strength
of the inner primary coating. The greater the cohesive strength of
the inner primary coating the greater the amount of energy required
to break apart the inner primary coating. Thus, an inner primary
coating having a higher cohesive strength can withstand greater
stripping forces during ribbon stripping without breaking apart and
leaving residue on the surface of the optical glass fiber, than an
inner primary coating having a lower cohesive strength.
[0239] The crack propagation can be measured as follows. First make
a 75 micron thick drawdown of the inner primary composition and
then cure the film by exposing it to 1.0 J/cm.sup.2 of UV from a
Fusion D lamp under a nitrogen atmosphere. Cut three test strips of
dimensions 35 mm long, 12 mm wide, and 75 micron thick. A cut 2.5
mm long is made in the side of each strip. A strip is mounted in a
RSA-II rheometer, the temperature brought to 90 C. (representative
ribbon stripping temperature), and a constant extension rate of 0.1
mm/second. is applied to the test strip. The measure of cohesive
strength is the increase in length L before the crack propagates
across the width of the test strip. The gauge length is constant at
23.2 mm. The value reported is currently the average of three
measurements.
[0240] The fiber pull-out friction of the inner primary coating is
an estimate of the fiber friction between the inner primary coating
and the bare optical glass fiber. In general, the. lower the fiber
pull-out friction of the inner primary coating the lower the fiber
friction between the optical glass fiber and the inner primary
coating, the lower the resistive force, and the easier the inner
primary coating will slide off of the optical glass fiber. Also,
the lower the fiber friction, the less force that will be applied
to the inner primary coating to conduct ribbon stripping. The less
the force being applied to the inner primary coating, the lower the
chance that the cohesiveness of the inner primary coating will
fail, thus leaving inner primary coating residue on the surface of
the optical glass fiber.
[0241] The fiber pull-out friction test can be performed as
follows. The sample consists of a bare, clean optical fiber, one
end of which has been embedded in a 250 micron thick sheet of cured
inner primary coating to be tested. This assembly is mounted in a
suitable instrument such as a Rheometrics RSA-II rheometer, and the
temperature raised to a representative ribbon stripping temperature
(such as 90.degree. C.), and the fiber pulled slowly out of the
sheet at a rate of 0.1 mm/sec. The instrument records and plots
force vs distance. The plots typically show a linear region of
negative slope, which is the result of a decreasing area of contact
between fiber and coating, as the fiber is being withdrawn. The
slope is measured, and is the output of the test. Low slope values
correspond to a low fiber pull-out friction, and vice versa. Three
test samples should be performed and their average used as the
final output of the test.
[0242] Prior to using the information from the crack propagation
and coefficient of friction measurements as a prediction method,
calibration is required. Calibration consists of obtaining test
data on at least five inner primary coatings of known cleanliness
performance, and fitting the data to a three-dimensional surface
using statistical procedures in a suitable statistical/plotting
computer program. A convenient two-dimensional representation of
the three-dimensional surface is a contour plot, in which each
contour represents a fixed value of the cleanliness rating, and the
vertical and horizontal axes are output values of the fiber
pull-out friction and crack propagation tests, respectively.
[0243] The cleanliness ratings should be expressed on a
quantitative scale, for example, a scale of 1 to 5. An example of a
suitable quantitative scale is the "Milli's" test described in the
background section herein above, the complete disclosure of which
is incorporated herein by reference. When referring to strip
cleanliness and predicted strip cleanliness herein, the numerical
values correspond to those of the Mill's test.
[0244] After the calibration contour plot has been obtained, a
point is plotted on it, using data from crack propagation and fiber
pull-out friction measurements of an inner primary coating
formulation for which a cleanliness prediction is desired. A
prediction of cleanliness is obtained by noting the position of the
point relative to the contour lines closest to it.
[0245] The following hypothetical example illustrates the
calibration step, and the use of the contour plot thus produced, to
obtain a predicted ribbon-stripping cleanliness. Eight inner
primary coatings A through H, are prepared, and coated on an
optical fiber in the usual manner, all having the same outer
primary coating over the respective inner primary coatings. Coated
fiber representing each of the eight inner primary coatings are
then coated with an ink layer, and then assembled into a ribbon
assembly. The type of ink and matrix material for ribbon assembly
should be identical for all eight specimens. Three ribbon
assemblies of each sample can be stripped at the desired ribbon
stripping temperature. The cleanliness of each sample is evaluated
using the Mill's test, in which 1 is best and 5 is worst. The final
rating for each of the eight specimens is the average of the
ratings of the three replicates. The hypothetical results are shown
in Table 5.
5TABLE 5 (HYPOTHETICAL) Fiber Crack Friction Propagation Coating
(g/mm) (mm) Rating A 2 1.1 1.6 B 30 0.8 5 C 35 1.6 3.7 D 20 1.7 2.8
E 7 2.3 1.8 F 25 2.0 1.5 G 4 1.6 1.6 H 22 1.0 3.9
[0246] Next, samples for fiber pull-out friction and crack
propagation are prepared from the inner primary coating made from
the selected inner primary composition, and output values for each
test obtained, by the methods described herein. At this point,
there are three data values associated with each of the eight
samples. Hypothetical values, chosen to be typical of actual cases,
are recorded in Table 5. The contour plot produced by a statistical
software program is shown in FIG. 6.
[0247] This contour plot is used as follows. For example, a sample
of an experimental inner primary coating is measured by the Fiber
Pull-Out Friction and Crack Propagation tests, and the resulting
data values were 10 and 1 respectively. The point corresponding to
those values is located on the contour plot, and it is seen to fall
between the contour values of 2.5 and 3. From its location relative
to the two lines, the predicted cleanliness rating is estimated to
be about 2.7.
[0248] A value of about 3 or less is considered acceptable for
optical glass fiber connections.
[0249] Viscosity Test Method
[0250] The viscosity was measured using a Physica MC10 Viscometer.
The test samples were examined and if an excessive amount of
bubbles was present, steps were taken to remove most of the
bubbles. Not all bubbles need to be removed at this stage, because
the act of sample loading introduces some bubbles.
[0251] The instrument was set up for the conventional Z3 system,
which was used. The samples were loaded into a disposable aluminum
cup by using the syringe to measure out 17 cc. The sample in the
cup was examined and if it contains an excessive amount of bubbles,
they were removed by a direct means such as centrifugation, or
enough time was allowed to elapse to let the bubbles escape from
the bulk of the liquid. Bubbles at the top surface of the liquid
are acceptable.
[0252] The bob was gently lowered into the liquid in the measuring
cup, and the cup and bob were installed in the instrument. The
sample temperature was allowed to equilibrate with the temperature
of the circulating liquid by waiting five minutes. Then, the
rotational speed was set to a desired value which will produce the
desired shear rate. The desired value of the shear rate is easily
determined by one of ordinary skill in the art from an expected
viscosity range of the sample.
[0253] The instrument panel read out a viscosity value, and if the
viscosity value varied only slightly (less than 2% relative
variation) for 15 seconds, the measurement was complete. If not, it
is possible that the temperature had not yet reached an equilibrium
value, or that the material was changing due to shearing. If the
latter case, further testing at different shear rates will be
needed to define the sample's viscous properties. The results
reported are the average viscosity values of three test
samples.
[0254] Tensile Strength, Elongation and Modulus Test Method
[0255] The tensile strength, elongation and modulus of cured
samples was tested using a universal testing instrument, Instron
Model 4201 equipped with a personal computer and software "Series
IX Materials Testing System." The load cells used were 2 and 20
pound capacity. The ASTM D638M was followed, with the following
modifications.
[0256] A drawdown of each material to be tested was made on a glass
plate and cured using a UV processor. The cured film was
conditioned at 22 to 24.degree. C. and 50+5% relative humidity for
a minimum of sixteen hours prior to testing.
[0257] A minimum of eight test specimens, having a width of
0.5.+-.0.002 inches and a length of 5 inches, were cut from the
cured film. To minimize the effects of minor sample defects, sample
specimens were cut parallel to the direction in which the drawdown
of the cured film was prepared. If the cured film was tacky to the
touch, a small amount of talc was applied to the film surface using
a cotton tipped applicator.
[0258] The test specimens were then removed from the substrate.
Caution was exercised so that the test specimens were not stretched
past their elastic limit during the removal from the substrate. If
any noticeable change in sample length had taken place during
removal from the substrate, the test specimen was discarded.
[0259] If the top surface of the film was talc coated to eliminate
tackiness, then a small amount of talc was applied to the bottom
surface of test specimen after removal from the substrate.
[0260] The average film thickness of the test specimens was
determined. At least five measurements of film thickness were made
in the area to be tested (from top to bottom) and the average value
used for calculations. If any of the measured values of film
thickness deviates from the average by more than 10% relative, the
test specimen was discarded. All specimens came from the same
plate.
[0261] The appropriate load cell was determined by using the
following equation:
[A.times.145].times.0.0015=C
[0262] Where: A=Product's maximum expected tensile strength
(MPa);
[0263] 145=Conversion Factor from MPa to psi;
[0264] 0.00015=approximate cross-sectional area (in.sup.2) of test
specimens; and
[0265] C=lbs.
[0266] The 2 pound load cell was used for materials where C=1.8 lbs
The 20 pound load cell was used for materials where 1.8<C<18
lbs. If C>19, a higher capacity load cell was required.
[0267] The crosshead speed was set to 1.00 inch/min (25.4 mm/min),
and the crosshead action was set to "return at break". The
crosshead was adjusted to 2.00 inches (50.8 mm) jaw separation. The
air pressure for the pneumatic grips was turned on and adjusted as
follows: set approximately 20 psi (1.5 Kg/cm.sup.2) for primary
optical fiber coatings and other very soft coatings; set
approximately 40 psi (3Kg/cm.sup.2) for optical fiber single coats;
and set approximately 60 psi (4.5 Kg/cm.sup.2) for secondary
optical fiber coatings and other hard coatings. The appropriate
Instron computer method was loaded for the coating to be
analyzed.
[0268] After the Instron test instrument had been allowed to
warm-up for fifteen minutes, it was calibrated and balanced
following the manufacturer's operating procedures.
[0269] The temperature near the Instron Instrument was measured and
the humidity was measured at the location of the humidity gage.
This was done just before beginning measurement of the first test
specimen.
[0270] Specimens were only analyzed if the temperature was within
the range 23.+-.1.0 C. and the relative humidity was within
50.+-.5%. The temperature was verified as being within this range
for each test specimen. The humidity value was verified only at the
beginning and the end of testing a set of specimens from one
plate.
[0271] Each test specimen was tested by suspending it into the
space between the upper pneumatic grips such that the test specimen
was centered laterally and hanging vertically. Only the upper grip
was locked. The lower end of the test specimen was pulled gently so
that it has no slack or buckling, and it was centered laterally in
the space between the open lower grips. While holding the specimen
in this position, the lower grip was locked.
[0272] The sample number was entered and sample dimensions into the
data system, following the instructions provided by the software
package.
[0273] The temperature and humidity were measured after the last
test specimen from the current drawdown was tested. The calculation
of tensile properties was performed automatically by the software
package.
[0274] The values for tensile strength, % elongation, and (secant
or segment) modulus were checked to determine whether any one of
them deviated from the average enough to be an "outlier." If the
modulus value was an outlier, it was discarded. If there were less
than six data values for the tensile strength, then the entire data
set was discarded and repeated using a new plate.
[0275] Elastic Modulus Test Method
[0276] The elastic modulus (E'), the viscous modulus (E"), and the
tan delta (E"/E'), which is an indication of the material's Tg, of
the examples were measured using a Rheometrics Solids Analyzer
(RSA-II), equipped with: 1) A personal computer having MS-DOS 5.0
operating system and having Rhios.RTM. software (Version 4.2.2 or
later) loaded; 2) A liquid nitrogen controller system for
low-temperature operation.
[0277] The test samples were prepared by casting a film of the
material, having a thickness in the range of 0.02 mm to 0.4 mm, on
a glass plate. The sample film was cured using a UV processor. A
specimen approximately 35 mm (1.4 inches) long and approximately 12
mm wide was cut from a defect-free region of the cured film. For
soft films, which tend to have sticky surfaces, a cotton-tipped
applicator was used to coat the cut specimen with talc powder.
[0278] The film thickness of the specimen was measured at five or
more locations along the length. The average film thickness was
calculated to +0.001 mm. The thickness cannot vary by more than
0.01 mm over this length. Another specimen was taken if this
condition was not met. The width of the specimen was measured at
two or more locations and the average value calculated to .+-.0.1
mm.
[0279] The geometry of the sample was entered into the instrument.
The length field was set at a value of 23.2 mm and the measured
values of width and thickness of the sample specimen were entered
into the appropriate fields.
[0280] Before conducting the temperature sweep, moisture was
removed from the test samples by subjecting the test samples to a
temperature of 80 C. in a nitrogen atmosphere for 5 minutes. The
temperature sweep used included cooling the test samples to about
-60 C. or about -80 C. and increasing the temperature at about
1/minute until the temperature reached about 60 C. to about 70 C.
The test frequency used was 1.0 radian/second.
[0281] Soluble Wax
[0282] Wax can be added as a slip agent to adjust the fiber
friction between the inner primary coating and the surface of the
optical glass fiber to a value that results in a resistive force
that is less than the cohesive strength of the inner primary
coating. However, conventional waxes exhibit incompatibility
problems with inner primary coatings. Many waxes do not dissolve
well in inner primary coatings and therefore they tend to separate
out from solution. Furthermore, conventional waxes tend to cause
the resulting inner primary coating to be hazy in appearance, which
is undesirable. The term "soluble wax" is used herein to designate
those waxes which are sufficiently soluble in the inner primary
coating composition at the concentration required to provide the
desired level of fiber friction. The term "wax" is understood to
include waxes as defined in Hawley's "Condensed Chemical
Dictionary", 11th edition, the said definition being incorporated
herein by reference.
[0283] It has been found that by selecting modified waxes or by
modifying the waxes, the incompatibility problems can be
substantially avoided. In selecting a modified wax, the solubility
of the modified wax in the desired inner primary composition should
first be considered. Usually, waxes tend to be insoluble in inner
primary coating compositions. The solubility of the wax in the
inner primary coating will depend mainly upon the following:
[0284] (1) the relative polarity of the wax and the polarity of the
monomers and oligomers present in the inner primary
composition,
[0285] (2) the respective types of functional groups present in the
wax and the monomers and oligomers present in the inner primary
composition, and
[0286] (3) the similarity between the molecular structure of the
wax and the oligomers or monomers present in the inner primary
composition, such as aliphatic/aromatic, unsaturated/saturated,
linear/branched, etc., entities.
[0287] For example, the solubility of the wax can be increased by
incorporating functional groups which are similar to those present
in the oligomers or monomers present in the inner primary
composition. If the inner primary composition contains monomers or
oligomers having ester groups, then ester groups can be
incorporated into the molecular backbone structure of the wax or
the ester groups can be grafted onto the backbone of the wax.
Alternatively, wax-like, long-chain fatty esters can be used.
Commercial examples of suitable fatty esters include:
[0288] Laneto-50 and 100 (PEG-75 lanolin),
[0289] Laneto-AWS (PPG-12-PEG-50 lanolin),
[0290] Ritacetyl (acetylated lanolin),
[0291] Ritahydrox (hydroxylated lanolin),
[0292] Ritasol (isopropyl lanolate),
[0293] Ritalan (lanolin oil),
[0294] Ritalan AWS (PPG-12-PEG-65-lanolin oil),
[0295] Ritawax (lanolin alcohol),
[0296] Supersat (hydrogenated lanolin),
[0297] Forlan C-24 (choleth-24 and Ceteth-24),
[0298] Ritachol 1000 (cetearyl alcohol, polysorbate 60,
PEG-150-stearate, and steareth-20),
[0299] Ritapro 100 (cetearyl alcohol, steareth-20, and
steareth-10),
[0300] Pationic ISL (sodium isostearoyl lactylate),
[0301] Pationic CSL (calcium stearoyl lactylate),
[0302] Pationic SSL (sodium stearoyl lactylate),
[0303] Pationic SBL (sodium behenoyl lactylate),
[0304] Pationic 138C (sodium lauroyl lactylate),
[0305] Pationic 122A (sodium caproyl lactylate),
[0306] Pationic SCL (sodium cocoyl lactylate),
[0307] Ritox 36 (laureth-23),
[0308] Ritox 52 (PEG-40 stearate),
[0309] Rita CA (cetyl alcohol),
[0310] Rita SA (stearyl alcohol), and
[0311] Rita Cetearyl Alcohol 70/30, (RITA Corp.). Preferably, the
fatty ester modified wax is isocetyl stearate.
[0312] If the inner primary composition contains monomers or
oligomers having alkoxy or hydroxy groups, then to increase the
solubility of the wax, alkoxy or hydroxy groups can be incorporated
into the molecular backbone structure of the wax or the alkoxy
groups can be grafted onto the backbone of the wax. Commercial
examples of such modified waxes include the Unilin.TM. series of
alcohol modified waxes from Petrolite, and
[0313] Ritawax (lanolin alcohol),
[0314] Ritachol 1000 (cetearyl alcohol, polysorbate 60,
PEG-150-stearate, and steareth-20),
[0315] Ritapro 100 (cetearyl alcohol, steareth-20, and
steareth-10),
[0316] Rita CA (cetyl alcohol),
[0317] Rita SA (stearyl alcohol), and
[0318] Rita Cetearyl Alcohol 70/30, (RITA Corp.). Preferably, the
alkoxy modified wax is
polypropyleneglycol.sub.12polyethyleneglycol.sub.50lanoli- n.
[0319] As another example, if the inner primary composition
contains monomers or oligomers having amine groups, then to
increase the solubility of the wax, amine groups can be
incorporated into the molecular backbone structure of the wax or
the amine groups can be grafted onto the backbone of the wax. An
example of such a modified wax is the Armeen.TM. series of amine
modified waxes (Armak), such as Armeen TD (tallowamine),
[0320] Armeen O, OL or OD (oleylamines),
[0321] Armeen SD (soyaamine),
[0322] Armeen 18 (octadecylamine),
[0323] Armeen HT, HTD or 2HT (hydrogenated tallow),
[0324] Armeen T or TM-97 (tallowamine),
[0325] Armeen 12D (dodecylamine),
[0326] Armeen C or CD (cocoamine),
[0327] Armeen 16D (hexadecylamine),
[0328] Armeen 2C (dicocoamine),
[0329] Armeen M2C (methyldicocoamine),
[0330] Armeen DM12D (dimethyldodecylamine),
[0331] Armeen DMCD or DMMCD (dimethylcocoamine),
[0332] Armeen DM14D (dimethyltetradecylamine),
[0333] Armeen DM16D (dimehylhexadecylamine),
[0334] Armeen DM18D (dimethyloctadecylamine),
[0335] Armeen DMHTD (dimethyl(hydrogenatedtallow)amine,
[0336] Armeen DMTD (dimethyltallow amine),
[0337] Armeen DMSD (dimethylsoyamine) or
[0338] Armeen DMOD (dimethyltallow amine). Preferably, the amine
substituted wax is methyl di(hydrogenated tallow)amine.
[0339] An example of a further functional group that can be
incorporated into the wax includes carboxylic acids. Suitable
examples of saturated modified waxes include capric acid, lauric
acid, myristic acid, palmitic acid, and stearic acid. Examples of
suitable unsaturated waxes include oleic acid, ricinoleic acid,
linoleic acid, and linolenic acid.
[0340] The functional groups present on the modified wax do not
necessarily have to be identical with those present in the
oligomers or monomers of the inner primary coating composition in
order to achieve increased solubility. Functional groups having
similar properties, such as hydrogen bonding, polarity, etc., can
be mixed and matched as desired to increase solubility.
[0341] The solubility of the wax can also be increased by modifying
a wax or selecting a wax having a similar molecular structure to
that of the monomers and oligomers present in the inner primary
composition. For example, if the monomers and oligomers contain
aromatic groups, the wax can be selected or modified to contain
aromatic groups. If the monomers or oligomers contain substantial
amounts of unsaturation, then the wax can be modified or selected
to contain substantial amounts of unsaturation. Furthermore, if the
monomers or oligomers are substantially linear, then a
substantially linear wax can utilized. Commercial examples of
substantially linear waxes include Polymekon, Ceramer 67 and 1608,
and Petrolite C-400, CA-11, WB-5, WB-11, and WB-17 (Petrolite).
[0342] Based on the teachings provided herein, one skilled in the
art will be able to modify or select the desired wax, and to use
the selected wax in an amount to provide the desired level of fiber
friction between the inner primary coating and the surface of the
optical glass fiber. The amount of the wax present in the inner
primary composition will depend on (1) the ability of the wax to
impart the desired reduction in the fiber friction between the
inner primary coating and the surface of the optical glass fiber,
and (2) the solubility of the wax in the inner primary composition.
The greater the solubility of the wax in the inner primary
composition, the greater the amount of wax that can be present. The
greater the ability of the wax to reduce fiber friction, the less
wax that will be required. Preferably, the amount of wax present is
about the minimum amount necessary to provide a level of fiber
friction necessary to result in a resistive force that provides a
clean, residue free optical glass fiber after ribbon stripping. As
discussed above, the fiber friction level that results a resistive
force level which will provide a clean, optical glass fiber after
ribbon stripping depends on the cohesive strength of the inner
primary coating. The greater the cohesive strength of the inner
primary coating, the greater the amount of resistive force that can
be tolerated and still provide a clean, bare optical glass fiber
after ribbon stripping. The amount of wax necessary to provide a
fiber friction that results in such a level of resistive force can
be readily determined by one skilled in the art by making test
samples of ribbon assemblies having different concentrations of the
selected wax in the inner primary coating. The amount of wax
required should be determined using complete ribbon structures
because, as discussed hereinabove, the presence of the outer
primary coating will have an effect on the strippability of the
inner primary coating.
[0343] Suitable amounts of wax can also be closely approximated by
using the fiber pull-out friction and crack propagation test
methods described herein, in which the amounts of wax that provide
a predicted strip cleanliness of less than about 3 are
preferred.
[0344] It has been found that suitable amounts of modified wax
include from about 0.01% to about 10% by weight of the total inner
primary composition, more preferably about 0.01% to about 5%, and
most preferably about 0. 01% to about 2%.
[0345] If desired, the wax can be further modified to include a
radiation-curable functional group that can copolymerize with
radiation-curable monomers and oligomers present in the inner
primary composition. An example of such a radiation-curable
functional wax is stearyl acrylate. The radiation-curable
functional group in general does not have to be an acrylate group,
but can be any known radiation-curable functional group, including
those described herein.
[0346] The invention will be further explained by the following
non-limiting examples illustrating the use of waxes.
EXAMPLES 3-1 THROUGH 3-4
[0347] The components shown in Table 6 were combined to form four
inner primary coating compositions. Drawdowns of the inner primary
coating compositions were made and then cured by exposure to UV
light from a Fusion D lamp, under a nitrogen atmosphere. The crack
propagation and fiber friction for each of the films were tested in
the same manner as above, and the predicted strip cleanliness was
calculated. The results are shown in Table 6.
6TABLE 6 COMPONENT (Amount in % by weight of total Example Example
Example Example composition 3-1 3-2 3-3 3-4 Linear Urethane
Acrylate 23 -- -- -- Oligomer Having a Weight Average Molecular
Weight of 5000, Urethane Acrylate Oligomer -- 51.9 42.3 42.3
H-I-PTGL2000-I-PTGL2000-I-H Lauryl Acrylate -- 16 -- -- Ethoxylated
Nonylphenol Acrylate 64.4 25.6 46.2 46.2 Glyceryl Propoxy
Triacrylate 8 -- -- -- Phenoxyethyl Acrylate -- -- 5 5
2,4,6,-Trimethyl 3 3 3 3 PhenylbenzoylDiphenyl Phosphine Oxide
Thiodiethylene bis (3,5-di-tert- .5 0.5 0.5 0.5 butyl-4-hydroxy)
hydrocinnamate Polyethylene/maleic anhydride .1 -- -- -- copolymer
wax (ceramer 1608) Methyl di (hydrogenated tallow) -- 2 -- -- Amine
Isocetyl Stearate -- -- 2 -- PPG.sub.12PEG.sub.50 Lanolin -- -- --
2 Mercaptopropyl Trimethoxy Silane 1 1 1 1 Test results Clarity
Clear Clear Clear Clear Viscosity (mPa .multidot. s, 25 C.) 7650
6760 7390 Fiber Friction (g/mm) 7.7 11.4 7.2 Crack Propagation (mm)
1.53 1.56 1.69 Predicted Strip Cleanliness 2.1 2.5 1.9 Fiber
Pull-out Residue Test 2.3 The oligomers were formed by reacting the
following components: H = Hydroxyethyl Acrylate I = Isophorone
Diisocyanate PTGL2000 = 2000 molecular weight
polymethyltetrahydrofurfuryl/polytetrahy- drofurfuryl copolymer
diol (Mitsui, NY), the methyl group provides branching which
reduces the orientation of the polymers formed from the
oligomer
[0348] The fiber pull-out residue test was the same test as used
previously except that the evaluation was quantified on a scale of
0 to 10, where 0 is the best (no visible residue under 10.times.
magnification) and 10 is the worst (lots of visible residue without
use of magnification).
[0349] The test results in Table 6 demonstrate that modified waxes
can be used to adjust the fiber friction to a level that provides a
resistive force less than the cohesive strength of the inner
primary coating, which is shown by the excellent predicted strip
cleanliness values of less than about 3.
[0350] Radiation-Curable, Silicone Containing Oligomers and Use of
Non-Radiation-Curable Silicone Compounds
[0351] Radiation-curable, silicone containing monomers and
oligomers can also be used to adjust the level of fiber friction
and thereby improve ribbon strippability of the inner primary
coating. The radiation-curable, silicone oligomer comprises a
silicone compound to which at least one radiation-curable
functional group is bound. Preferably, two or more
radiation-curable functional groups are connected to the silicone
entity.
[0352] Preferably the radiation-curable functional group is capable
of copolymerizing with the radiation-curable monomers and oligomers
present in the inner primary composition when exposed to suitable
radiation. Therefore, the selection of the functional group will
depend on the monomer or oligomer present in the inner primary
composition. One skilled in the art will readily be able to
determine which functional groups will cross-link with the monomer
or oligomer present in the inner primary composition. While not
being limited thereto, examples of suitable functional groups are
groups containing vinyl, acrylate, methacrylate, maleate, vinyl
ether, or acrylamides, as well as those described herein above.
[0353] Examples of commercially available silicone compounds
containing a radiation-curable functional group are silicone
acrylates Ebecryl 350 and Ebecryl 1360 (Radcure Industries), Tego
Rad 2100, 2200, 2500, and 2600 (Tego Chemie), and Coat-O-Sil 3503
(OSI Specialties).
[0354] Alternatively, based on the teachings herein, one skilled in
the art will be able to modify known silicone compounds to include
the required radiation-curable functionality. For example, a
silicone compound provided with hydroxy functionality can be
reacted with a diisocyanate compound and a compound containing a
hydroxy and a radiation-curable functionality to provide a
radiation-curable functionality to said silicone compound. Specific
examples include reacting a silicone compound containing a hydroxy
functionality with a diisocyanate and hydroxyethylacrylate to
provide an acrylate functionality on the silicone compound, or
isocyanate and hydroxybutylvinylether to provide a vinyl ether
functionality on the silicone compound. Example of suitable
silicone compound containing hydroxyl functionality include:
polydimethylsiloxane diol of 1200 equivalent weight Q4-3667, DC 193
and DC 1248 (Dow Corning), HSi2111 (Tego Chemie), and Coat-O-Sil
3500 and 3505 (Osi Specialties).
[0355] Alternatively, non-radiation-curable silicone compounds
(hereinafter referred to as "non-reactive silicone") can be used to
adjust the fiber friction and thereby improve ribbon strippability
of the inner primary coating.
[0356] U.S. Pat. No. 4,496,210, which is incorporated herein by
reference, discloses examples of suitable non-reactive silicones
that can be used. Non-reactive silicones can be used separately or
in conjunction with the radiation-curable silicone oligomers
described herein.
[0357] The radiation-curable silicone oligomer and/or non-reactive
silicone should be present in an amount to provide a fiber friction
that results in a resistive force that is less than the cohesive
strength of the inner primary composition. The amount of
radiation-curable silicone oligomer and/or non-reactive silicone is
preferably the minimum amount required to provide a fiber friction
that results in a resistive force less than the cohesive strength
of the inner primary composition. Such minimum amount can easily be
determined by making test runs of inner primary compositions in
which the amount of radiation-curable silicone oligomers and/or
non-reactive silicones present is varied. The lowest amount of
radiation-curable silicone oligomers and/or non-reactive silicones
present which provides a fiber friction that results in a resistive
force that is less than the cohesive strength. of the inner primary
coating is the preferred amount.
[0358] A long chain silicone compound containing on average about
one radiation-curable functional group (monofunctional) bound near
a terminus of the silicone compound can provide further advantages.
The end of the long silicone chain furthest from the
radiation-curable functional group can be mechanically bound in the
inner primary coating. However, upon heating during ribbon
stripping, it is believed that the end of the long silicone chain
farthest from the radiation-curable functional group can become
unbound and diffuse toward the optical glass fiber/inner primary
coating interface which is in the direction the heat is
propagating. This diffusion of silicone increases at the critical
moment during ribbon stripping to facilitate the clean removal of
the entire coating system. The silicone acts as a lubricant between
the surface of the optical glass fiber and the inner primary
coating.
[0359] The thickness of an inner primary coating usually varies
from about 10 microns to about 35 microns. Thus, a
mono-functionalized silicone fluid having a molecular chain length
of about 50,000 to about 350,000 Daltons can diffuse toward the
glass/inner primary coating interface during ribbon stripping.
[0360] Suitable amounts of radiation-curable silicone oligomers
and/or non-reactive silicones can also be closely approximated by
using the friction and crack propagation test methods described
herein, in which the amounts of radiation-curable silicone
oligomers and/or non-reactive silicones that provide a predicted
strip cleanliness of less than about 3 are preferred.
[0361] The amount of radiation-curable silicone oligomer and/or
non-reactive silicones will also depend on the selection of the
inner primary composition, in particular the initial fiber friction
of the selected inner primary coating composition. Generally, the
higher the initial fiber friction (no slip additive), the greater
the amount of radiation-curable silicone oligomer and/or
non-reactive silicone that will be required to lower the fiber
friction to a level that provides a resistive force lower than the
cohesive strength of the inner primary coating.
[0362] In general, the radiation-curable silicone oligomers can be
used in greater amounts than non-reactive silicones because it is
believed that the radiation-curable silicone oligomer will become
bound in the inner primary coating during curing, whereas the
non-reactive silicone is free to migrate throughout the cured inner
primary coating. Alternatively, the radiation-curable silicone
oligomer can be the main oligomer used for forming the inner
primary coating. It has been found that suitable amounts of
radiation-curable silicone oligomer are between about 0.1 to about
90% by weight, preferably about 0.1 to about 60% by weight, and
more preferably about 0.1 to about 30% by weight. In general,
higher molecular weight radiation-curable silicone oligomers will
be present in a radiation-curable coating in greater weight
percentages than lower molecular weight composite oligomers.
[0363] Suitable amounts of mono-functionalized monomers have been
found to be about 0.1 to about 20% by weight, more preferably about
0.1 to about 10% by weight, and most preferably about 0.1 to about
5% by weight.
[0364] Suitable amounts of non-reactive silicone are between about
0.01 to about 10% by weight, preferably about 0.01 to about 5% by
weight, and more preferably about 0.01 to about 1% by weight.
[0365] The invention will be further explained by the following
non-limiting examples illustrating the use of silicone
entities.
EXAMPLE 4-1
[0366] The components shown in Table 7 were combined to form an
inner primary coating composition. A film of the coating material
(75 micron thick) was prepared on glass slides and then cured by
exposure to UV light in the same manner as above. The tensile
strength, elongation and modulus were measured.
[0367] A 75 micron film of the coating material was also prepared
and suitably cured. The crack propagation was then measured. A
friction test was also conducted, as described herein. The
predicted ribbon strip cleanliness was calculated. The results are
shown in Table 7.
7 TABLE 7 Component (Amount is % by weight of total Example
composition) 4-1 Oligomer H-DesW-PTHF2900-DesW-H 47.5 Ethoxylated
Nonylphenol Acrylate 29 Lauryl Acrylate 14.2 2,4,6-Trimethyl
Phenylbenzoyl Diphenyl 3 Phosphine Oxide Silicone Oligomer 5
H-I-HSi2111-I-H y-Mercaptopropyltrimethoxy Silane .8 Thiodiethylene
Bis (3,5-di-tert-Butyl-4- .5 Hydoxy) Hydocinnamate Test Results
Viscosity, mPa .multidot. s (25 C.) 6040 Tensile Strength, Mpa 1
Elongation, % 140 Modulus, Mpa 1.4 Dose at 95%, Modulus, J/Sq CM
.38 Crack Propagation (mm) 1.7 Fiber Pull-Out Friction (g/mm) 17.1
Predicted Strip Cleanliness 2.5-3 The oligomers were formed by
reacting the following components: H = Hydroxyethyl Acrylate DesW =
bis 4,4-(isocyanatocyclohexyl) methane I = Isophorone Diisocyanate
PTHF2900 = 2900 molecular weight Polytetramethylene Ether (BASF)
HSi2111 = a silicone diol having a MW of 1000 (Tego Chemie)
EXAMPLES 4-2 THROUGH 4-10
[0368] The components shown in Table 8 were combined to form 11
different inner primary coating compositions. The viscosity and
clarity of the compositions was determined.
[0369] Films of the coating materials (75 micron thick) were
prepared on microscope slides and then cured by exposure to UV
light in the same manner as above. The tensile strength, elongation
and modulus were measured.
[0370] Additional films of the coating materials were also prepared
and suitably cured. The crack propagation was then measured. A
friction test was also conducted, as described herein. The
predicted ribbon strip cleanliness was calculated. The results are
shown in Table 8.
8TABLE 8 Component (Amount is % by weight of Ex. Ex. Ex. Ex. Ex.
Ex. Ex. Ex. Ex. total composition) 4-2 4-3 4-4 4-5 4-6 4-7 4-8 4-9
4-10 Oligomer 45.67 H-I-PTHFCD2000-I- PTHFCD2000-I-H Oligomer 54.86
H-(I-PPG1025) 1.06-(- PERM) 1.14-I-H Oligomer 60.65
H-I-PTGL2000-I-H Oligomer 67.5 70 H-I-PPG2010-I-PPG2010-I-H
Oligomer 51.02 49.23 43 H-I-PTGL2000-I-PTGL2000-I-H Oligomer 78
(H-I).sub.3-TPE4542 Ethoxylated Nonylphenol 34.48 24.99 32.85 20.14
24.75 16 50.5 Acrylate Ester Lauryl Acrylate 14.35 13.72 6.92 16.64
Isodecyl Acrylate Phenoxyethyl Acrylate 16.62 2.5 Mole Propoxylated
Nonyl 25.00 23.5 Phenol Acrylate 25:75 weight/weight of 2.94 3 Bis
(2,6- Dimnethoxybenzoyl) (2,4,4- Trimethylpentyl) Phosphine Oxide
and 2-Hydroxy-2- Methyl-1-Phenyl Propanone 2,4,6-trimethylbenzoyl 3
2.5 3 3 1 3 Diphenyl Phosphine Oxide 1-Hydroxycyclohexyl Phenyl 4
Ketone Octadecyl 3,5-Bis(1,1- .5 .5 Dimethylethyl)-4-
Hyroxybenzenepropanone Thiodiethylene bis(3,5-di- .49 .5 .3 .5
Tert-Butyl-4- Hydroxy) hydrocinnamate Ditridecylthiodipropionate 1
1 Free Silicone, DC-193 (Dow 1 2 1 2 2 Corning) Free Silicone,
DC-190 (Dow 1 Corning) Teograd 2100 silicone 2.5 1 5 acrylate L-77
Polyethylene oxide modified Dimethylsiloxane 1-Propanethiol,3- 1 1
.98 1 1 1 .92 1 1 (Trimethoxysilyl) Clarity When Made clear clear
clear clear clear Clarity After 24 Hours at clear clear clear
4.degree. C. Clarity After 24 Hours at clear clear clear
-20.degree. C. Clarity After 3 Days at clear clear clear 60.degree.
C. Viscosity (mPa .multidot. s, 8700 5600 8000 9520 7170 6240 8200
25.degree. C.) Dose @ 95% Modulus .77 .46 .45 .32 .36 .45 .2 J/sq.
cm) Tensile Strength (MPa) .4 1.5 .6 1.1 Elongation (%) 50 100 140
180 Modulus (Mpa) 1.2 2.7 1.1 1.3 2.4 Fiber Friction (g/mm) 3.1 4.9
2.7 4.4 21 18.4 18.5 3 3.4 Fiber Friction (g/mm) After 1 1.4 7
days, 60.degree. C., dose 95% of dose required for complete cure
Crack Propagation (mm) 2.1 1.49 1 1.4 1.21 1.82 1.47 1.1 1.9 Crack
Propagation (mm) 1.1 after 7 days, 60.degree. C., dose 95 of dose
required for complete cure Predicted Strip Cleanliness 1.5-2 1.5
2.2 1.5 3.6 3 3 1.5 1.5 The oligomers were formed by reacting the
following components: H = Hydroxyethyl Acrylate I = Isophorone
Diisocyanate PTHFCD2000 = is PolyTHF containing some carbonate
linkages PPG1025 = is Polypropyleneoxidediol having an average
molecular weight of 1000 (Arco) PPG2010 = is Polypropyleneoxidediol
having an average molecular weight of 2000 (BASF) PTGL2000 = 2000
molecular weight
polymethyltetrahydrofurfuryl/polytetrahydrofurfuryl copolymer diol
(Mitsui, NY) TPE4542 = polypropylene glycol ethylene oxide
endcapped triol (BASF) Perm = Permanol KM10-1733
polycarbonate/polyether copolymer diol
[0371] The test results in Table 8 demonstrate that the
radiation-curable silicone oligomers and non-reactive silicones can
be used to adjust the fiber friction to a level that provides a
resistive force less than the cohesive strength of the inner
primary coating, which is shown by the predicted strip cleanliness
values of about 3 or less.
[0372] Radiation-Curable Fluorinated Oligomers and Fluorinated
Materials
[0373] The fiber friction between the inner primary coating and the
surface of the optical glass fiber can also be significantly
reduced by incorporating radiation-curable fluorinated oligomers,
monomers and/or non-radiation curable fluorinated materials into
the inner primary coating composition. The radiation-curable,
fluorinated oligomer or monomer comprises a fluorinated compound to
which at least one radiation-curable functional group is bound.
Preferably, two or more radiation-curable functional groups are
connected to the fluorinated entity.
[0374] Preferably the radiation-curable functional group is capable
of copolymerizing with the radiation-curable monomers and oligomers
present in the inner primary composition when exposed to suitable
radiation. Therefore, the selection of the functional group will
depend on the monomer or oligomer present in the inner primary
composition. One skilled in the art will easily be able to
determine which functional groups will cross-link with the monomer
or oligomer present in the inner primary composition. While not
being limited thereto, examples of suitable radiation-curable
functional groups are groups containing vinyl, acrylate,
methacrylate, maleate, vinyl ether, or acrylamides, as well as
those described herein above.
[0375] Examples of commercially available fluorinated compounds
containing at least one radiation-curable functional group include
perfluoro ethyl acrylate (DuPont), 2-(N-Ethylperfluoro Octane
Sulfonamido)Ethyl Acrylate (3M), 1H,1H-pentadecafluoroctyl acrylate
(Oakwood Research Chemicals), as well as methacrylate or N butyl
acrylate versions of these.
[0376] Based on the teachings herein, one skilled in the art will
be able to modify a fluorinated compound to include the required
radiation-curable functionality. For example, a fluorinated
compound provided with hydroxy functionality can be reacted with a
diisocyanate compound and a compound containing a hydroxy and a
radiation-curable functionality to provide a radiation-curable
functionality to said fluorinated compound. Specific examples
include reacting a fluorinated compound containing a hydroxy
functionality with a diisocyanate and hydroxyethylacrylate to
provide an acrylate functionality on the fluorinated compound, or
isocyanate and hydroxybutylvinylether to provide a vinyl ether
functionality on the fluorinated compound. Examples of suitable
fluorinated compounds containing hydroxyl functionality include
Fluorolink E (Ausimont), 2-methyl-4,4,4-trifluorobutanol,
1H,1H-pentadecafluoro-1-octanol, 1H,1H-pentafluoropropanol-1, and
1H,1H,12H,12H-perfluoro-1,12-dodecanediol (Oakwood Research
Chemicals).
[0377] Alternatively, non-radiation-curable fluorinated compounds
(hereinafter referred to simply as "fluorinated compounds") can be
used to adjust the fiber friction and thereby improve ribbon
strippability of the inner primary.
[0378] The fluorinated compounds can be used separately or in
conjunction with the radiation-curable silicone oligomers or
monomers described herein.
[0379] The radiation-curable fluorinated oligomer or monomer and/or
fluorinated compounds should be present in an amount to provide a
fiber friction that results in a resistive force that is less than
the cohesive strength of the inner primary composition. The amount
of radiation-curable fluorinated oligomer and/or fluorinated
compound is preferably the minimum amount required to provide a
fiber friction that results in a resistive force less than the
cohesive strength of the inner primary composition. Such minimum
amount can easily be determined by making test runs of inner
primary compositions in which the amount of radiation-curable
fluorinated oligomers or monomers and/or fluorinated present is
varied. The lowest amount of radiation-curable fluorinated
oligomers or monomers and/or fluorinated compounds present which
provides a fiber friction that results in a resistive force less
than the cohesive strength of the inner primary coating is the
preferred amount.
[0380] Suitable amounts of radiation-curable fluorinated oligomers
or monomers and/or fluorinated compounds can also be closely
approximated by using the friction and crack propagation test
methods described herein, in which the amounts of radiation-curable
fluorinated oligomers or monomers and/or fluorinated compounds that
provide a predicted strip cleanliness of less than about 3 are
preferred.
[0381] The amount of radiation-curable fluorinated oligomer or
monomers and/or fluorinated compounds will also depend on the
selection of the inner primary composition, in particular the
initial fiber friction of the selected inner primary coating
composition. Generally, the higher the initial fiber friction (no
slip additive), the greater the amount of radiation-curable
fluorinated oligomer or monomer and/or fluorinated compounds that
will be required to lower the fiber friction to a level that
provides a resistive force lower than the cohesive strength of the
inner primary coating.
[0382] In general, the radiation-curable fluorinated oligomers or
monomers can be used in greater amounts than non-reactive
fluorinated compounds because it is believed that the
radiation-curable fluorinated oligomers or monomers will become
bound in the inner primary coating during curing, whereas the
non-reactive fluorinated compounds are free to migrate throughout
the cured inner primary coating. Alternatively, the
radiation-curable fluorinated oligomer or monomer can be the main
oligomer used for forming the inner primary coating. It has been
found that suitable amounts of radiation-curable fluorinated
oligomer or monomer are between about 0.1 to about 90% by weight,
preferably about 0.1 to about 60% by weight, and more preferably
about 0.1 to about 30% by weight. In general, larger molecular
weight oligomers can be used in greater amounts than lower
molecular weight oligomers or monomers.
[0383] Suitable amounts of fluorinated compounds have been found to
be between about 0.01 to about 10% by weight, preferably about 0.01
to about 5% by weight, and more preferably about 0.01 to about 1%
by weight.
[0384] The invention will be further explained by the following
non-limiting examples illustrating the use of fluorinated
materials.
EXAMPLES 5-1 THROUGH 5-3
[0385] The components shown in Table 9 were combined to form 5
different inner primary coating compositions. The viscosity and
clarity of the compositions were determined.
[0386] Films of the coating materials (75 micron thick) were
prepared on glass slides and then cured by exposure to UV light in
the same manner as above. The tensile strength, elongation and
modulus were measured.
[0387] Additional films of the coating materials were also prepared
and suitably cured. The crack propagation was then measured. A
friction test was also conducted, as described herein. The
predicted ribbon strip cleanliness was calculated. The results are
shown-in Table 9.
9TABLE 9 Component (% by weight based Ex. Ex. Ex. on total
composition) 5-1 5-2 5-3 Oligomer 54.32 55.58
H-(I-PPG1025).sub.1.06-(-PERM).sub.1.14-I-H Oligomer
H-(I-PPG2010).sub.2-I-H 67.75 Ethoxylated Nonylphenol 24.74 25.31
Acrylate Ester Isodecyl Acrylate 13.58 13.9 2.5 Mole Propoxylated
Nonyl 25 Phenol Acrylate 25:75 weight/weight of 2.91 3 Bis (2,6-
Dimethoxybenzoyl) (2,4,4- Trimethylpentyl) Phosphine Oxide and
2-Hydroxy-2-Methyl- 1-Phenyl Propanone 1-Hydroxycyclohexyl Phenyl 4
Ketone Octadecyl 3,5-Bis (1,1- 0.50 Dimethylethyl)-4-
Hyroxybenzenepropanone Thiodiethylene bis (3,5-di- .48 .5
tert-butyl-4- hydroxy) Hydrocinnamate Ditridecylthiodipropionate
1.00 Foralkyl EM-6 3.00 Tridecafluorooctyl Mecaptan (Elf Autochem)
Fluorosulfonamide (3M) 0.75 .75 mercaptopropyl trimethoxy 0.97 1 1
silane Clarity as made Clear Clear Clear Clarity after 24 hours at
4.degree. C. Clear Clarity after 24 hours at - Clear 20.degree. C.
Clarity after 3 days at 60.degree. C. Very Few Incom pat's
Viscosity (mPa .multidot. s, 25 C.) 6200 Dose @ 95% Modulus (J/sq
.multidot. cm) .77 0.50 .47 Tensile Strength (MPa) 0.50 Elongation
(%) 88 Modulus (MPa) 1.20 Fiber Friction (g/mm) 25.5 8.2 10.5 Fiber
Friction (g/mm) After 7 1.1 days, 60 C., at dose of 95% of dose for
complete cure Crack Propagation (mm) 1.32 1.54 1.1 Crack
Propagation (mm) after 7 1 days, 60 C., at dose of 95% of dose for
complete cure Predicted Strip Cleanliness 3.0 2.0 2.6 Table Notes:
The oligomers were formed by reacting the following components: H =
Hydroxyethyl Acrylate; I = Isophorone Diisocyanate PPG1025 = is
Polypropyleneoxidediol having an average molecular weight of 1000
(Arco) PPG2010 = is Polypropylenediol having an average molecular
weight of 2000 (BASF) PTGL2000 = 2000 molecular weight
polymethyltetrahydrofurfuryl/ polytetra-hydrofurfuryl copolymer
diol (Mitsui, NY) Perm = Permanol KM10-1733 polycarbonate/polyether
copolymer diol
[0388] Solid Lubricants
[0389] Surprisingly, it has been found that solid lubricants can be
added to the inner primary composition to reduce the fiber friction
between the inner primary coating and the surface of the optical
glass fiber. The term "solid lubricant" is used herein to mean that
the lubricant is substantially insoluble in the inner primary
composition and that the particle or flake shape of the solid
lubricant is substantially maintained after curing of the inner
primary coating composition.
[0390] Usually the solid lubricant is non-reactive with the
components of inner primary coating composition. Examples of
suitable non-reactive solid lubricants are the following, but not
limited thereto:
[0391] solid organic lubricants including organic polysaccarides
such as sodium alginate, polyolefins, polyvinyl alcohol, nylon such
as orgasol (Elf Atochem), solid Teflon particles, and hard waxes
such as Rad Wax; solid inorganic lubricants including molybdenum
disulfide, graphite, silicates such as talc, clays such as kaolin
and mica, silica, and boron nitride.
[0392] However, if desired, a reactive solid lubricant can be used.
Reactive solid lubricants contain a radiation-curable functional
group. Preferably, the radiation-curable functional group is
capable of copolymerizing with the radiation-curable monomers or
oligomers present in the inner primary composition. The
radiation-curable functional group can be, for example, any of the
radiation-curable functional groups described herein. Specific
examples of suitable reactive solid lubricants include zinc
acrylate, molybdenum acrylate, aluminum acrylate, barium acrylate,
and chromium acrylate.
[0393] The particle size is preferably small enough to avoid
microbending caused by the solid particles exerting stresses on the
surface of the optical glass fiber during use. Furthermore, the
particle size is preferably small enough to avoid causing the inner
primary coating to be hazy in appearance. Examples of suitable
particle sizes have been found to be about 10 microns or less,
preferably about 5 microns or less, and most preferably less than
about 2 microns.
[0394] Alternatively to the particle size, the hardness of the
solid lubricant is preferably low enough to avoid microbending
caused by the solid particles exerting stresses on the surface of
the optical glass fiber during use. In general, a softer solid
lubricant will be less likely to cause such microbending.
[0395] Based on the teachings provided herein, one skilled in the
art will easily be able to use the selected solid lubricant in an
amount to provide the desired level of fiber friction between the
inner primary coating and the surface of the optical glass fiber.
The amount of the solid lubricant present in the inner primary
composition will depend on the ability of the solid lubricant to
impart the desired reduction in the fiber friction between the
inner primary coating and the surface of the optical glass fiber,
and the amount the fiber friction must be reduced to provide a
fiber friction level that results in a resistive force less than
the cohesive strength of the inner primary coating. In general, the
greater the ability of the solid lubricant to reduce fiber
friction, the less solid lubricant that will be required.
Preferably, the amount of solid lubricant present is about the
minimum amount necessary to provide a level of fiber friction
necessary to provide a clean, residue free optical glass fiber
after ribbon stripping. As discussed above, the fiber friction
level that will provide a clean, optical glass fiber after ribbon
stripping will depend on the cohesive strength of the inner primary
coating. The greater the cohesive strength of the inner primary
coating, the greater the amount of fiber friction, and resulting
resistive force, that can be tolerated and still provide a clean,
bare optical glass fiber after ribbon stripping. The amount of
solid lubricant necessary to provide such a level of fiber friction
can be easily determined by one skilled in the art by making test
samples of ribbon assemblies having different concentrations of the
selected solid lubricant in the inner primary coating. The amount
of solid lubricant required should be determined using complete
ribbon structures because, as discuss herein above, the presence of
the outer primary coating will have an effect on the strippability
of the inner primary coating.
[0396] Suitable amounts of solid lubricant can also be closely
approximated by using the fiber pull-out friction and crack
propagation test methods described herein, in which the amounts of
solid lubricant that provides a predicted strip cleanliness of less
than about 3 are preferred.
[0397] It has been found that suitable amounts of solid lubricant
include from about 0.1% to about 20% by weight of the total inner
primary composition, more preferably about 0.1% to about 10%, and
most preferably about 0.1% to about 5%.
[0398] Preferably, a surfactant is used in combination with the
solid lubricant. Examples of a suitable surfactants include:
fluorosulfonamide surfactant (3M), 3,6-dimethyl-4-octyne-3,6-diol
(Air Products), linear copolymer of vinylpyrolidone and long chain
alpha olefin (International Specialty Products), Solsperse high Mw
polymeric dispersing agents (Zeneca), and other well-known anionic,
cationic and non-ionic surfactants.
[0399] The invention will be further explained by the following
non-limiting examples.
EXAMPLES 6-1 THROUGH 6-3
[0400] The components shown in Table 10 were combined to form 8
different inner primary coating compositions. The viscosity and
clarity of the compositions was determined.
[0401] Films of the coating materials (3 mil) were prepared on
microscope slides and then cured by exposure to UV light in the
same manner as above. The tensile strength, elongation and modulus
were measured.
[0402] 75 mm films of the coating materials were also prepared and
suitably cured. The crack propagation was then measured. A fiber
pull-out friction test was also conducted, as described herein. The
predicted ribbon strip cleanliness was calculated. The results are
shown in Table 10.
10TABLE 10 Component (Amount is % by weight of total Ex. Ex. Ex.
composition) 6-1 6-2 6-3 Oligomer H-(I-PTGL2000).sub.2-I-H 36.1
42.3 36.1 Ethoxylated Nonylphenol Acrylate 44.4 46.1 43.9
Phenoxyethyl Acrylate 5 5 5 2,4,6-trimethylbenzoyl Diphenyl 3 3 3
Phosphine Oxide and 2-Hydoxy-2- Methyl-1-Phenyl-1-Propanone blend
Thioethylene bis (3,5-di-tert- .5 .5 .5 butyl-4-Hydroxy)
Hydrocinnamate y-Mercaptopropyltrimethoxy 1 1 1 Silane Rad Wax 62EB
(33% PE wax in 10 epoxy acrylate) Fluorosulfonamide Surfactant FC-
.1 .5 430 (3M) Fluoro A (Micronized PTFE) 2 10 Test results Clarity
(opaque?) yes yes yes Color white white white Viscosity, mPa
.multidot. s at 25.degree. 5440 7960 7520 Film Opacity, 3 mil
opaque cloudy cloudy Fiber Friction (g/mm) 15.2 8.2 6.6 Crack
Propagation (mm) 1.96 2.2 Predicted Strip Cleanliness 2.2 2.4 The
oligomers were formed by reacting the following components: H =
Hydroxyethyl Acrylate I = Isophorone Diisocyanate PTGL2000 = 2000
molecular weight
polymethyltetrahydrofurfuryl/polytetrahydrofurfuryl copolymer diol
(Mitsui, NY) Perm = Permanol KM10-1733 polycarbonate/polyether
copolymer diol
[0403] The test results in Table 10 demonstrate that solid
lubricants can be used to reduce the friction to a level that
results in a resistive force less than the cohesive strength of the
inner primary coating, which is shown by the predicted strip
cleanliness values of about 3 or less.
[0404] Use of Novel Slip Agents
[0405] The above described novel slip agents can be used alone, in
combinations of novel slip agents, as novel slip agents with
conventional slip agents, and as novel slip agents in combination
with the adjusting the normal force as desired to provide the
desired level of fiber friction.
[0406] Based on the above experimental data, the composition of the
inner primary coating can surprisingly be formulated or selected to
provide a fiber friction of about 40 (g/mm) or less, preferably
about 30 (g/mm) or less, and more preferably about 20 (g/mm), and
most preferably about 10 (g/mm) or less at the desired ribbon
stripping temperature, in combination with a crack propagation of
the inner primary coating which is greater than about 0.7 mm,
preferably greater than about 1 mm, more preferably greater than
about 1.5 mm, and most preferably greater than about 2 mm, at the
desired/design ribbon stripping temperature, such as 90.degree. C.
Table 11 and example 11-1 illustrates a practice according to this
invention.
11TABLE 11 Component (% weight based on total weight of
composition) Example 11-1 Oligomer H-(I-PTGL2000).sub.2-I-H 50.3
Isobornyl Acrylate 10 Ethoxylated Nonylphenol Acrylate Ester 15.1
Thiodiethylene bis (3,5-di-tert-butyl-4-Hydroxy) 0.5 Hydrocinnamate
Phenoxy Ethyl Acrylate 20 2,4,6-Trimethylbenzoyl Diphenyl Phosphine
Oxide 3 Silicone Fluid.sup.1 0.1 gamma-Mercaptopropyl Trimethoxy
Silane 1 Test Results Predicted Strip Cleanliness 2.5 Fiber
Friction (g/mm) 18.5 Crack Propagation (mm) 2.07 The oligomers and
monomers were formulated from the following components: H =
Hydroxyethylacrylate I = Isophoronediisocyanate PTGL2,000 =
polymethyltetrahydrofurfuryl/p- olytetrahydrofurfuryl copolymer
diol having the molecular weight (2,000), (Mitsui, NY) Silicone
Fluid = Byk333 (BYK Chemie) which is polydimethylsiloxane with
terminal polyethylene oxide groups
[0407] Linear Oligomers
[0408] If desired, ribbon strippability can also be improved by
increasing the ability of the inner primary coating to transmit
force applied during ribbon stripping. In general, the more
efficient the inner primary coating is at transmitting the force
applied during the ribbon stripping operation, the less stripping
force that need be applied to remove the inner primary coating.
[0409] It has now also been found that the use of linear oligomers
can improve the effectiveness, and consequently the efficiency, of
the inner primary coating to transmit the ribbon stripping forces
applied during ribbon stripping operations. In general, to the
extent that the molecular structure of the oligomer is designed to
be more linear, the more densely the oligomers will pack together
when forming the inner primary coating. It has been found that as
the oligomers become more densely packed, the more efficiently the
inner primary coating can transmit the stripping force applied
during ribbon stripping.
[0410] The ability of a ribbon assembly to strip cleanly during
ribbon stripping can be further improved if the polymers bound in
the outer primary coating have the ability to orient upon
heating.
[0411] Examples of linear, radiation-curable oligomers according to
the present invention that provide enhanced strippability can be
illustrated by the following formula (4):
R.sup.1-L-[R.sup.2-L].sub.n-R.sup.3 (4)
[0412] wherein: R.sup.1 and R.sup.3 are organic groupings having
radiation-curable functional groups as defined herein, and R.sup.2
is an optional organic radical;
[0413] L is a linking group, providing a bridging group such as a
urethane, thio-urethane, urea or ester grouping, as defined herein,
preferably urethane;
[0414] R.sup.2 is a substantially linear carbon-containing entity;
and
[0415] n is about 1 to about 40, preferably about 1 to about 20,
and most preferably about 1 to about 10, wherein the molecular
weight of [R.sup.2-L].sub.n. is about 500 to about 20,000,
preferably about 1,000 to about 10,000, and most preferably about
1,500 to about 6,000.
[0416] When n is 1, [R.sup.2-L] can contain, for example, a
polyolefin, polyether, polycarbonate, or polyester structure.
having a molecular weight of about 500 to about 20,000. When n is
from about 2 to about 5, [R.sup.2-L] can include a polyolefin,
polyether, polycarbonate, or polyester having a molecular weight of
about 500 to about 10,000. When n is from about 5 to about 30,
[R.sup.2-L] can represent a polyolefin, polyether, polycarbonate,
or polyester having a molecular weight of about 500 to about
4,000.
[0417] The linear oligomers according to this invention can be used
in an amount suitable to provide the desired level of ribbon
stripping performance. The desired amount can easily be found and
determined by one skilled in the art by testing different amounts
of the selected linear oligomer(s) in an inner primary coating, and
optionally in an outer primary coating as well, on optical glass
fibers encased in a ribbon assembly. It has generally been found
that the linear oligomers according to this invention can be used
in amounts of about 0.1 to about 90 wt. %, preferably about 5 to
about 80 wt. %, more preferably about 5 to about 60 wt. %, based on
the total weight of the inner primary or outer primary
composition.
EXAMPLE 7-1 THROUGH 7-2
[0418] The components shown in Table 12 were combined to form an
inner primary coating composition. The compositions were cured and
the fiber pull-out friction of the cured coating was measured, as
defined herein. The test results are shown in Table 12.
12TABLE 12 Component (Amount is % by weight of total Example
Example composition) 7-1 7-2 Oligomer H-(I-PTHF2000),-I-H 52.26
52.26 Ethoxylated Nonylphenol Acrylate 15.7 15.67 Lauryl Acrylate
15.19 16.19 n-Vinyl Formamide Isobornyl Acrylate 11.8 0 n-Vinyl
Formamide Ethylhexyl Acrylate 0 10.8 25:75 weight/weight of
Bis(2,6- 3.7 3.7 Dimethoxybenzoyl) (2,4,4-Trimethylpentyl)
Phosphine Oxide and 2-Hydroxy-2-Methyl-1- Phenyl Propanone
gamma-Mercaptopropyl Trimethyoxy 0.92 0.92 Silane Thioethylene
Bis(3,5 di-tert-butyl-4- .46 .46 hydroxyl) Hydrocinnamate
(antioxidant) Test Results Fiber Pull-Out Residue Test 0.875 1.25
The oligomer was formed by reacting the following components: H =
Hydroxyethyl Acrylate I = Isophorone Diisocyanate PTHF2000 = 2000
molecular weight Polytetramethylene Ether Glycol (BASF)
[0419] Terminal-Linear Moieties
[0420] It has been found that the use of radiation-curable
oligomers containing at least one terminal linear moiety can also
improve the efficiency of the inner primary coating to transmit the
stripping force applied during the ribbon stripping operation.
[0421] Examples of radiation-curable oligomers according to the
present invention that provide enhanced strippability can be
illustrated by the following formula:
R.sup.4-x-L-x-[R.sup.5-x-L-x].sub.n-R.sup.6
[0422] wherein
[0423] R.sup.4 is a substantially linear long chain alkyl
terminating in at least one hydroxyl group;
[0424] each L represents, independently, a molecular bridging
group, preferably derived from a diisocyanate precourser
reactant;
[0425] each x represents a resulting reacted linking group, such
as, inter alia, a urethane, thio-urethane, or urea entity.
[0426] Alternatively, ester linkages can also be utilized;
[0427] R.sup.5 is a linear or a branched or cyclic hydrocarbon or
polyether moiety derived from a a diol and having a molecular
weight of from 150 to 10,000, preferably from 500 to 5,000, and
most preferably from 1,000 to 2,000 Daltons;
[0428] R.sup.6 is an end group carrying a radiation-curable
functional group as defined herein, preferably an acrylate or
methacrylate, and also having an hydroxyl linkage to the L
entity.
[0429] R.sup.4 preferably has at least about 80%, more preferably
at least about 90%, of its carbon atoms in a straight chain;
and,
[0430] n may represent a number from zero to 30.
[0431] Preferably, R.sup.4 is an alkyl radical with of from about
C.sub.9 to about C.sub.20, since longer carbon chains may decrease
the resistance against oil. Suitable examples of alkyls are lauryl,
decyl, isodecyl, tridecyl, and stearyl. Most preferred is
lauryl.
[0432] R.sup.5 can contain a branched or cyclic aliphatic group
having about 6 to about 15 carbon atoms. In particular R.sup.5 can
be the aliphatic component of a diisocyanate compound such as
isophorone diisocyanate, DesW, TMDI, and HXDI. If R.sup.5 is a
branched component, preferably, the extent of branching units is at
least about 10 mole %, and more preferably at least about 20 mole
%, based on the total number of carbon atoms in R.sup.5.
[0433] The oligomers according to above formula can be made, for
example, by reacting in a first reaction one mole of a diisocyanate
compound (for forming R.sup.5) with (1) one mole of a long chain
alkyl containing a hydroxy group (for forming R.sup.4) or (2) one
mole of a compound containing a hydroxy functional group and a
radiation-curable functional group (for forming R.sup.6). The
urethane linking group "x" attached to "L" is formed by the
reaction of the isocyanate group with a hydroxyl group. In a second
reaction, the remaining isocyanate group is reacted with the other
as yet unreacted hydroxyl group of the compound. Reactions of
hydroxy functional compounds with isocyanate functional molecules
are well known in the art, and can be catalyzed if needed, with
known catalysts. Suitable examples of reactants containing a
radiation-curable functional group and a hydroxy group are
hydroxyethylacrylate or 2-hydroxypropylacrylate. Suitable examples
of linear long chain alkyls include lauryl alcohol, decyl alcohol,
isodecyl alcohol, tridecyl alcohol, and stearyl alcohol.
[0434] The resulting radiation-curable oligomer can be used in
optical glass fiber coatings, in particular in inner primary
coatings, as a monomer that enhances the strippability of the final
coating, and that yields a coating composition which may have a
high cure speed.
[0435] The radiation-curable oligomers according to this invention
can accordingly be used in amounts suitable to. provide the desired
level of ribbon stripping performance. The desired amount can
easily be determined by one skilled in the art by simple testing of
different amounts of the selected linear oligomer(s) in an inner
primary coating, and optionally in an outer primary coating as
well, on optical glass fibers encased in a ribbon assembly. It has
been found that the oligomers provided by this invention can
generally be used in amounts of about 1 to about 90 wt. %,
preferably about 5 to about 80 wt. %, and most preferably about 5
to about 60 based on the total weight of the inner primary or outer
primary composition.
EXAMPLE 8-1 AND COMPARATIVE EXAMPLES H-1 THROUGH H-3
[0436] The components shown in Table 13 were combined to inner
primary coating compositions.
[0437] 75 micron thick films of the coating materials were prepared
and suitably cured. The fiber pull-out friction test was conducted,
as described herein, and the test results are shown in Table
13.
13TABLE 13 Component Comp. Comp. Comp. (Amount is % by weight of
total Example Example Example Example composition) H-1 H-2 H-3 8-1
Oligomer H-(I-PTHF2000).sub.2-I-H 52.26 52.26 52.56 52.56
Ethoxylated Nonylphenol 15.67 15.67 15.67 15.67 Acrylate Lauryl
Acrylate 3.39 10.79 10.79 7.15 n-Vinyl Formamide Isobornyl 23.6 0 0
0 Acrylate n-Vinyl Formamide Ethylhexyl 0 16.2 21.6 0 Acrylate
n-Vinyl Formamide Butyl 0 0 0 19.84 Acrylate 25:75 weight/weight of
Bis(2,6- 3.7 3.7 3.7 3.7 Dimethoxybenzoyl) (2,4,4- Trimethylpentyl)
Phosphine Oxide and 2-Hydroxy-2-Methyl-1- Phenyl Propanone
gamma-Mercaptopropyl 0.92 0.92 0.92 0.92 Trimethyoxy Silane
Thioethylene Bis(3,5 di-tert- 0.46 0.46 0.46 0.46 butyl-4-hydroxyl)
Hydrocinnamate (antioxidant) Test Results Fiber Pull-Out Residue
Test 1.5 0.75 1 0.65 The oligomer was formed by reacting the
following components: H = Hydroxyethyl Acrylate I = Isophorone
Diisocyanate PTHF2000 = 2000 molecular weight Polytetramethylene
Ether Glycol (BASF)
[0438] The test results in Table 13 demonstrate that as the length
of the linear moiety is increased, the fiber pull-out friction
decreases.
[0439] Aromatic Groups
[0440] Ribbon strippability can also be enhanced by incorporating a
high concentration of aromatic groups in the oligomers and monomers
used to form the inner primary coating. It will be appreciated that
coating compositions comprising about 0.1 or more moles of aromatic
groups per 100 grams of total composition, calculated using the
molecular weights of the compositional components, are regarded as
having a high concentration of aromatic groups. It is believed that
the planarity of the phenyl ring next to the surface of the optical
glass fiber may allow for the good slidability of the inner primary
coating off the optical glass fiber during ribbon stripping.
EXAMPLE 9-1
[0441] The components shown in Table 14 were combined to form an
inner primary coating composition.
[0442] A 75 micron thick film of the coating material was prepared
and suitably cured. The crack propagation was then measured. A
friction test was also conducted, as described herein. The results
are shown in Table 14.
14 TABLE 14 Component (Amount is % by weight of total Example
composition) 9-1 Oligomer H-I-(PTGL2000-I).sub.2-H 51.54
Ethoxylated Nonylphenol Acrylate 20.86 Phenoxyethyl Acrylate 16.8
Lauryl Acrylate 7 25:75 weight/weight of Bis(2,6- 2.5
Dimethoxybenzoyl) (2,4,4- Trimethylpentyl) Phosphine Oxide and 2-
Hydroxy-2-Methyl-1-Phenyl Propanone Thiodiethylene
Bis(3,5-di-tert-butyl- 0.3 gamma-hydroxy) Hydrocinnamate
gamma-Mercaptopropyl Trimethoxy Silane 1 Test Results Crack
Propagation (mm) 1.49 Fiber Pull-Out Friction (g/mm) 10 Predicted
Strip Cleanliness 2 The oligomer was formed by reacting the
following components: H = Hydroxyethyl Acrylate I = Isophorone
Diisocyanate PTGL2000 = 2000 molecular weight
polymethyltetrahydrofurfuryl/polytetrahydrofurfuryl copolymer diol
(Mitsui, NY)
[0443] High Molecular Weight Polymeric Blocks and Reduced
Concentration of Urethane
[0444] Radiation-curable, inner primary optical glass fiber coating
compositions (hereinafter referred to as "inner primary
compositions") are now well known in the art. Such inner primary
compositions usually contain at least one radiation-curable
oligomer, and optionally reactive diluents, photoinitiators, and
additives, as described herein above.
[0445] It has now been found that by reformulating the
radiation-curable oligomer used in the inner primary composition,
an inner primary coating can be formed having a significantly
increased crack propagation in combination with a significantly
decreased fiber friction. Furthermore, it has been found that the
crack propagation can be increased and the fiber friction decreased
to levels which provide the inner primary coating with the ability
to strip cleanly from the surface of an optical glass fiber during
ribbon stripping, without the use of substantial amounts of slip
agents in the inner primary coating. In some instances, the use of
slip agents can be substantially avoided. The term slip agents
includes components which are separate and distinct from the
radiation-curable oligomer as well as slip agent moieties that can
be bound to the radiation-curable oligomer. The use of slip agents
may cause undesirable delamination of the inner primary coating
during use of the ribbon assembly in hot and wet environments, such
as tropical environments, which can lead to microbending and
attenuation of the signal transmission. Thus, by substantially
avoiding the use of slip agents to provide a ribbon-strippable
inner primary coating, the present invention can provide a
ribbon-strippable inner primary coating which exhibits enhanced
resistance to such undesirable delamination.
[0446] Radiation-curable, oligomers comprising a carbon containing
backbone to which at least one radiation-curable functional group
is bound are well known in the art. Usually, the carbon containing
backbone of the radiation-curable oligomer contains one or more
polymeric blocks each having a molecular weight up to about 2000
and being connected together via coupling groups. Thus, an oligomer
having a molecular weight of about 6000, will usually contain three
polymeric blocks each having a molecular weight of about 2000 which
are connected via coupling groups. The radiation-curable functional
groups are also usually connected to the carbon-containing backbone
via coupling groups.
[0447] By extensive experimentation, it has now been found that as
the molecular weight of the polymeric blocks is increased, the
crack propagation of the inner primary coating increases. and the
fiber friction of the inner primary coating decreases. The
molecular weight of the polymeric blocks should be adjusted up to
level which provides an inner primary coating having a fiber
friction and crack propagation that are suitable for ribbon
stripping. For example, the molecular weight of the polymeric block
can be adjusted upward to level which provides an inner primary
coating having a combination of fiber friction and crack
propagation that provides a predicted strip cleanliness of about 3
or less, and preferably about 2 or less. Alternatively, the
molecular weight of the polymeric block can be adjusted upward to
level which provides an inner primary coating having a fiber
friction of about 30 g/mm or less at a rate of 0.1 mm/sec in
combination with a crack propagation of at least about 1.3 mm at a
rate of 0.1 mm/sec, at a ribbon stripping temperature. Preferably,
the fiber friction is about 25 g/mm or less and more preferably
about 20 g/mm or less. Preferably, the crack propagation is at
least about 1.5 mm and more preferably at least about 2 mm. The
crack propagation is usually below about 4, but can be higher.
[0448] It has been found that by using polymeric blocks having a
molecular weight greater than 2000, preferably at least about 2500,
and most preferably at least about 3000, inner primary coatings
having a fiber friction and a crack propagation as described above
can be provided. The molecular weight of said polymeric block is
usually less than about 10,000, preferably less than about
8,000.
[0449] The coupling groups can be any group capable of providing a
link between polymer blocks and/or between radiation-curable
functional groups and polymer blocks. Examples of suitable coupling
groups are urethane, urea and thiourethane. For purposes of
practicing the present invention, which relates to adjusting the
crack propagation and fiber friction using the molecular weight of
the polymeric blocks and/or urethane concentration, the following
groups are not considered coupling groups when determining the
molecular weight of the polymeric blocks: carbonate, ether, and
ester groups. Thus, when determining the molecular weight of the
polymeric block, ether groups, carbonate groups, and ester groups
are considered part of the polymeric block. Polymeric compounds
separated by urethane, thiourethane and urea groups are considered
separate polymeric blocks. Urethane is the preferred coupling
group.
[0450] Usually, urethane groups are used as the coupling groups in
the radiation-curable oligomer. For example, if an oligomer having
a number average molecular weight about 6000 comprising 3 polymer
blocks, each having a number average molecular weight of about
2000, and containing 2 radiation-curable functional groups, will
have four urethane linkages. Two of the urethane linkages connect
the radiation-curable groups to the polymeric blocks and two of the
urethane linkages connect the three polymeric blocks together.
[0451] It has now been found that as the concentration of urethane
linkages present in the inner primary composition is decreased, the
crack propagation of the inner primary coating increases and the
fiber friction of the inner primary coating decreases. Thus, the
term urethane concentration represents the weight percentage of all
urethane linkages present in the inner primary coating composition,
based on the total weight. of the inner primary coating
composition.
[0452] Based on this discovery, the urethane concentration should
be adjusted downward to a level which provides an inner primary
coating having a fiber friction and crack propagation that are
suitable for ribbon stripping the desired ribbon assembly. For
example, the urethane concentration can be adjusted downward to a
level which provides an inner primary coating having a combination
of fiber friction and crack propagation that provides a predicted
strip cleanliness of about 3 or less, and preferably about 2 or
less. It has been found that if the concentration of urethane
linkages-is about 4% by weight or less, inner primary coatings
having a fiber friction and a crack propagation that exhibit a
predicted strip cleanliness of about 3 or less can be provided.
Preferably, the urethane concentration is about 3.5% by weight or
less, more preferably about 2.5% or less by weight, and most
preferably about 2% or less by weight. The urethane concentration
effect on fiber friction and crack propagation is more pronounced
for higher molecular weight oligomers, such as about 3,000 to about
10,000, more preferably about 3,500 to about 8,000. Thus,
preferably the urethane oligomer has a molecular weight of about
3,000 to about 10,000 in combination with a urethane concentration
of about 4% by weight or less, more preferably, a molecular of
about 3,500 to about 8,000 in combination with a urethane
concentration of about 3.5% or less, and most preferably, a
molecular weight of about 3,500. to about 8,000 in combination with
a urethane concentration of about 3% or less.
[0453] The polymeric blocks can comprise for example polyethers,
polyolefins, polycarbonates, polyesters, polyamides or copolymers
thereof. Preferably, the polymeric blocks comprise polyethers.
[0454] The radiation-curable functional groups used can be any
functional group capable of polymerization when exposed to actinic
radiation. Suitable radiation-curable functional groups are now
well known and within the skill of the art.
[0455] Commonly, the radiation-curable functionality used is
ethylenic unsaturation, which can be polymerized through radical
polymerization or cationic polymerization. Specific examples of
suitable ethylenic unsaturation are groups containing acrylate,
methacrylate, styrene, vinylether, vinyl ester, N-substituted
acrylamide, N-vinyl amide, maleate esters, and fumarate esters.
Preferably, the ethylenic unsaturation is provided by a group
containing acrylate, methacrylate, or styrene functionality, and
most preferably acrylate or methacrylate.
[0456] Another type of radiation-curable functionality generally
used is provided by, for example, epoxy groups, or thiol-ene or
amine-ene systems. Epoxy groups can be polymerized through.
cationic polymerization, whereas the thiol-ene and amine-ene
systems are usually polymerized through radical polymerization. The
epoxy groups can be, for example, homopolymerized. In the thiol-ene
and amine-ene systems, for example, polymerization can occur
between a group containing allylic unsaturation and a group
containing a tertiary amine or thiol.
[0457] The radiation-curable oligomer can be easily formed by
reacting a polymeric polyol, a compound containing a
radiation-curable functional group and a hydroxyl group, and a
polyisocyanate. The general reaction of isocyanate functional
groups with hydroxyl groups to form urethane linkages is well known
in the art. Thus, one skilled in the art will be able to make the
improved oligomer according to the present invention based on the
disclosure provided herein.
[0458] Examples of suitable polymeric polyols that can be used to
form the radiation-curable oligomer include polyether diols,
polyolefin diols, polyester diols, polycarbonate diols, and
mixtures thereof. Polyether and polycarbonate diols, or
combinations thereof, are preferred. The polymeric block is the
residue of the polymeric polyol after reaction to form the
radiation-curable oligomer.
[0459] If a polyether diol is used, preferably the polyether is a
substantially non-crystalline polyether. Preferably, the polyether
comprises repeating units of one or more of the following monomer
groups: 1
[0460] Thus, suitable polyethers can be made from epoxy-ethane,
epoxy-propane, tetrahydrofuran, methyl-substituted tetrahydrofuran,
epoxybutane, and the like. Commercial examples of a suitable
polyether polyols that can be used are PTGL2500, PTGL3000,
PTGL3500, and PTGL4000 (Hodogaya Chemical Company).
[0461] If a polyolefin diol is used, the polyolefin is preferably a
linear or branched hydrocarbon containing a plurality of hydroxyl
end groups. The hydrocarbon provides a hydrocarbon backbone for the
oligomer. Preferably, the hydrocarbon is a non-aromatic compound
containing a majority of methylene groups (--CH.sub.2--) and which
can contain internal unsaturation and/or pendent unsaturation.
Examples of suitable hydrocarbon diols include, for example:
hydroxyl-terminated;
[0462] fully or partially hydrogenated 1,2-polybutadiene;
copolymers of 1,4-polybutadiene;
[0463] copolymers of 1,2-polybutadiene;
[0464] polyisobutylene polyol;
[0465] mixtures thereof, and the like. Preferably, the hydrocarbon
diol is a substantially, fully hydrogenated
1,2-polybutadiene-ethene copolymer or 1,2-polybutadiene-ethene
copolymer.
[0466] Examples of polycarbonate diols are those conventionally
produced by the alcoholysis of diethylene carbonate with a
diol.
[0467] Examples of polyester diols include the reaction products of
saturated polycarboxylic acids, or their anhydrides, and diols.
Commercial examples are the polycaprolactones, commercially
available from Union Carbide under the trade designation Tone
Polylol series of products, for example, Tone 0200, 0221, 0301,
.0310, 2201, and 2221. Tone Polyol 0301 and 0310 are
trifunctional.
[0468] Any organic polyisocyanate, alone or in admixture, can be
used as the polyisocyanate. Examples of suitable diisocyanates
include: isophorone diisocyanate (IPDI);
[0469] toluene diisocyanate. (TDI);
[0470] diphenylmethylene diisocyanate;
[0471] hexamethylene diisocyanate;
[0472] cyclohexylene diisocyanate;
[0473] methylene dicyclohexane diisocyanate;
[0474] 2,2,4-trimethyl hexamethylene diisocyanate;
[0475] m-phenylene diisocyanate;
[0476] 4-chloro-1,3-phenylene diisocyanate;
[0477] 4,4'-biphenylene diisocyanate;
[0478] 1,5-naphthylene diisocyanate;
[0479] 1,4-tetramethylene diisocyanate;
[0480] 1,6-hexamethylene diisocyanate;
[0481] 1,10-decamethylene diisocyanate; 1,4-cyclohexylene
diisocyanate; and
[0482] polyalkyloxide and polyester glycol diisocyanates such as
polytetramethylene ether glycol terminated with TDI and
polyethylene adipate terminated with TDI, respectively. Preferably,
the isocyanates are TDI or IPDI.
[0483] If other oligomers, monomers, and/or additives containing
urethane linkages are used in admixture with the above described
radiation-curable oligomer to form an inner primary composition,
the concentration of urethane linkages present in each other
oligomer, monomer or additive should be included in the urethane
concentration calculation. Examples of common monomers containing
urethane linkages include:
[0484] trimethylolpropane triacrylate, the triacrylate or
methacrylate from hexane-2,4,6 triol, or from glycerol, ethoxylated
glycerol, or propoxylated glycerol,
[0485] hexanediol diacrylate,
[0486] 1,3-butylene glycol diacrylate,
[0487] neopentyl glycol diacrylate,
[0488] 1,6-hexanediol diacrylate,
[0489] neopentyl glycol diacrylate,
[0490] polyethylene glycol-200 diacrylate,
[0491] tetraethylene glycol diacrylate, triethylene glycol
diacrylate,
[0492] pentaerythritol tetraacrylate,
[0493] tripropylene glycol diacrylate,
[0494] ethoxylated bisphenol-A diacrylate,
[0495] trimetylolpropane diacrylate,
[0496] di-trimethylolpropane tetraacrylate,
[0497] triacrylate of tris(hydroxyethyl) isocyanurate,
dipentaerythritol hydroxypentaacrylate,
[0498] pentaerythritoltriacrylate,
[0499] ethoxylated trimethylolpropane triacrylate,
[0500] triethylene glycol dimethacrylate,
[0501] ethylene glycol dimethacrylate,
[0502] tetraethylene glycol dimethacrylate,
[0503] polyethylene glycol-2000 dimethacrylate,
[0504] 1,6-hexanediol dimethacrylate,
[0505] neopentyl glycol dimethacrylate,
[0506] polyethylene glycol-600 dimethacrylate,
[0507] 1,3-butylene glycol dimethacrylate,
[0508] ethoxylated bisphenol-A dimethacrylate, trimethylolpropane
trimethacrylate,
[0509] diethylene glycol dimethacrylate,
[0510] 1,4-butanediol diacrylate,
[0511] diethylene glycol dimethacrylate,
[0512] pentaerythritol tetramethacrylate,
[0513] glycerin dimethacrylate,
[0514] trimethylolpropane dimethacrylate,
[0515] pentaerythritol trimethacrylate,
[0516] pentaerythritol dimethacrylate,
[0517] pentaerythritol diacrylate, and
[0518] the like and mixtures thereof.
[0519] Mono(meth)acrylates such as cyclohexyl(meth)acrylate,
[0520] isobornyl(meth)acrylate,
[0521] lauryl(meth)acrylate,
[0522] alkoxylated phenolacrylate,
[0523] isooctyl-acrylate,
[0524] 2-ethylhexyl-acrylate,
[0525] hydroxyethyl acrylate, and
[0526] tetrahydrofurfuryl(meth)-acrylate.
[0527] The Invention will be further explained by the following
non-limiting examples illustrating the use of block polymeric
formulations.
EXAMPLES 10-1 THROUGH 10-14 AND COMPARATIVE EXAMPLES J-1 THROUGH
J-11
[0528] Inner primary compositions were made by combining the
components shown in Tables 15 and 16, in the same manner as
described herein above. The viscosity of the compositions was
measured as described above, and the results are shown in Tables 15
and 16. The inner primary compositions were cured by exposure to UV
radiation and the fiber friction and crack propagation properties
were measured, in the same manner as described herein above. The
test results are shown in Tables 15 and 16.
15TABLE 15 Component (% by weight of Ex. Ex. Ex. Ex. Ex. Ex. Ex.
Ex. Ex. Ex. Ex. Ex. Ex. Ex. total composition) 10-1 10-2 10-3 10-4
10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 Oligomer
H-I-PPG3025-I-H 49.38 0 0 0 0 0 0 0 0 0 0 0 0 0 Oligomer
H-I-PPG4025-I-H 0 49.38 0 0 0 0 0 0 0 0 0 0 0 0 Oligomer
H-I-PTGL3000-I-H 0 0 64.38 0 0 49.38 0 0 0 0 0 0 0 0 Oligomer
H-I-PTGL3500-I-H 0 0 0 64.38 0 0 49.38 0 0 39.38 45.23 45.23 65.33
64.68 Oligomer H-I-PTGL4000-I-H 0 0 0 0 64.38 0 0 49.38 0 0 0 0 0 0
Oligomer H-(I-PTGL2000).sub.a- 0 0 0 0 0 0 0 0 50.54 0 0 0 0 0 I-H
Phenoxy Ethyl Acrylate 0 0 0 0 0 0 0 0 14 0 25.13 20.1 20.1 17.91
Ethoxylated Nonylphenol 40.32 40.32 25.32 25.32 25.32 40.32 40.32
40.32 15.16 50.21 25.13 20.1 0 0 Acrylate Ester Isobornyl Acrylate
0 0 0 0 0 0 0 0 10 0 0 10.5 10.5 6.97 Lauryl Acrylate 6 6 6 6 6 6 6
6 6 5.99 0 0 0 5.97 Thiodiethylene bis (3,5-di- .3 .3 .3 .3 .3 .3
.3 .3 .3 .3 .3 .3 .3 .3 tert-butyl-4-Hydroxy) Hydrocinnamate
2,4,6-Trimethylbenzoyl 3 3 3 3 3 3 3 3 0 0 0 0 0 0 Diphenyl
Phosphine Oxide and 2-Hydroxy-2-Methyl-1- Phenyl-1-Propanone
2-Hydroxy-2-Methyl-1- 0 0 0 0 0 0 0 0 3 3 3 3 3 3
Phenyl-1-Propanone Bis (2,6-Dimethoxybenzyl)
(2,4,4-Trimethylpentyl) Phosphine Oxide gamma-Mercaptopropyl 1 1 1
1 1 1 1 1 1 1 1 1 1 Trimethoxy Silane Test Results Viscosity mPa
.multidot. s (25.degree. C.) 1200 1190 25350 321350 16840 9380
17680 7050 5570 4530 7220 5540 10670 9440 Urethane Concentration
2.01 1.76 2.99 2.65 2.24 2.29 2.03 1.72 2.67 1.62 1.86 1.86 2.69
2.66 (%).sup.1 Fiber Pull-Out Friction 19.3 10.8 23.23 21.27 27.63
21.84 14.04 16.15 25.3 13.4 15.8 15.2 25.6 21.6 (g/mm) Crack
Propagation (mm) 1.5 2.18 1.66 1.63 1.82 1.76 2.32 2.31 2.04 2.6 2
2.9 1.6 1.8 .sup.1The urethane concentration can be calculated from
(1) the amount of NCO present in the urethane linkages of the
oligomer, (2) the molecular weight of the oligomer, which can be
measured by conventional methods, and (3) the amount of oligomer in
the composition. The polyol molecular weights in Table I are
estimated rather than measured molecular weights.
[0529]
16TABLE 16 Component (% by weight based on Comp. Comp Comp Comp
Comp Comp Comp Comp Comp Comp. Comp. total weight Ex. Ex. Ex. Ex.
Ex. Ex. Ex. Ex. Ex. Ex. Ex. of composition) J-1 J-2 J-3 J-4 J-5 J-6
J-7 J-8 J-9 J-10 J-11 Oligomer H-I-PTGK2000-I-H 0 83.7 68.7 79.7
79.7 74.7 69.7 67.7 79.7 49.38 64.38 Oligomer
H-(I-PERM1000).sub.1.4- 56 0 0 0 0 0 0 0 0 0 0
(I-PPG1025).sub.1.06-I-H isodecyl acrylate 14 HI 0 0 0 0 0 5 10 15
0 0 0 Phenoxy Ethyl Acrylate 0 0 5 0 10 10 7 0 0 0 Ethoxylated
Nonylphenol 25.5 6 21 0 0 0 0 0 0 40.32 25.32 Acrylate Ester
Isobornyl Acrylate 0 0 0 5 10 0 0 0 10 0 0 Lauryl Acrylate 0 6 6 6
6 6 6 6 6 6 6 Thiodiethylene bis (3,5-di- .5 .3 .3 .3 .3 .3 .3 .3
.3 .3 .3 tert-butyl-4-Hydroxy) Hydrocinnamate
2,4,6-Trimethylbenzoyl 0 3 3 3 3 3 3 3 0 3 3 Diphenyl Phosphine
Oxide and 2-Hydroxy-2-Methyl-1- Phenyl-1-Propanone
2-Hydroxy-2-Methyl-1- 3 0 0 3 3 3 3 3 3 0 0 Phenyl-1-Propanone Bis
(2,6-Dimethoxybenzyl) (2,4,4-Trimethylpentyl) Phosphine Oxide
gamma-Mercaptopropyl 1 1 1 1 1 1 1 1 1 1 1 Trimethoxy Silane Test
Results Viscosity mPa .multidot. s (25.degree. C.) 6000 5050 10310
Urethane Concentration (%) 4.9 5.38 4.42 5.12 5.12 5.31 5.49 5.87
5.12 3.53 4.30 Fiber Pull-Out Friction 44 41.97 34.84 41.8 40.2
44.6 40.4 39.9 44.9 34.84 41.17 (g/mm) Crack Propagation (mm) 1
1.32 1.45 1.21 1.25 1.05 1.2 1.17 1.2 1.45 1.32 The oligomers in
Tables 15 and 16 were formulated from the following components: H =
Hydroxyethylacrylate I = Isophoronediisocyanate HI = Hexane
diisocyanate PTGL2000 =
polymethyltetrahydrofurfuryl/polytetrahydrofurfuryl copolymer diol
having the molecular weight of 2000 (Mitsui, NY) PPG1025 =
polypropyleneoxide diol having an average molecular weight of 1025
(BASF) Perm 1000 = Permanol KM10-1733 polycarbonate/polyether
copolymer diol having an average molecular weight of 1000
[0530] As can be seen from Examples 10-6 through 10-8, and
Comparative Example J-10, as the concentration of urethane
decreases, the crack propagation increases and the fiber friction
decreases. Furthermore, as the molecular weight of the polymeric
blocks increases, the crack propagation increases and the fiber
friction decreases.
[0531] Similarly, as can be seen from Examples 10-3 through 10-5,
and Comparative Example J-11, as the concentration of urethane
decreases, the crack propagation increases and the fiber friction
decreases. Furthermore, as the molecular weight of the polymeric
blocks increases, the crack propagation increases and the fiber
friction decreases. Examples 10-3 through 10-5 used significantly
more of the radiation-curable oligomer than Examples 10-6 through
10-8, and the same trend in fiber friction and crack propagation
was clearly demonstrated. Based on this experimental evidence, the
trend in fiber friction and crack propagation is dependent mainly
upon the oligomer. Furthermore, these Examples used a polyether
polymeric block.
[0532] Examples 10-1 and 10-2 demonstrate that when a polypropylene
oxide polymeric block is used as a polyether polymeric block, the
crack propagation and fiber friction are still dependent upon the
molecular weight of the polymeric block and/or the concentration of
urethane if used. In particular, as the concentration of urethane
decreases, the crack propagation increases and the fiber friction
decreases. Furthermore, as the molecular weight of the polymeric
blocks increases, the crack propagation increases and the fiber
friction decreases.
[0533] Examples 10-4, 10-7 and 10-10 through 10-14 used different
amounts of the same radiation-curable oligomer. The experimental
results demonstrate that the trend in crack propagation and fiber
friction is based on the molecular weight of the polymeric block
and/or the concentration of urethane.
[0534] The test results in Table 15 demonstrate that the above
described trends regarding crack propagation and fiber friction
based on molecular weight and/or urethane concentration are
independent of the type of oligomers and is generally consistent
among the different types of oligomers.
[0535] FIG. 7 illustrates a graph which includes the data shown in
Tables 15 and 16, above. As can be seen from FIG. 7, the urethane
concentration in the inner primary composition directly affects the
fiber pull-out friction. As the urethane concentration is
decreased, the fiber pull-out friction is decreased.
[0536] FIG. 8 illustrates a graph of the fiber friction versus
urethane concentration for Examples 10-10 through 10-14. FIG. 8
clearly demonstrates the direct correlation between fiber pull-out
friction and urethane concentration in the inner primary
composition. In particular, as the urethane concentration decreases
the fiber pull-out friction decreases.
EXAMPLES 10-15 THROUGH 10-22
[0537] Inner primary compositions were made by combining the
components shown in Table 17, in the same manner as described.
herein above. The viscosity of the compositions was measured as
described above, and the results are shown in Table 17. The inner
primary compositions were cured by exposure to UV radiation and the
fiber friction and crack propagation properties were measured, in
the same manner as described herein above. The test results are
shown in Table 17.
17TABLE 17 Component (% by weight based on total weight Exmp. Exmp.
Exmp. Exmp. Exmp. Exmp. Exmp. Exmp. of composition) 10-15 10-16
10-17 10-18 10-19 10-20 10-21 10-22 Oligomer
H-(I-PTGL2000).sub.2-I-H 23.71 28.45 33.19 37.93 42.68 47.42 52.16
56.9 Phenoxy Ethyl Acrylate 64.68 58.52 52.35 46.19 40.03 33.86
27.7 21.53 Ethoxylated Nonylphenol 7.11 8.53 9.95 11.38 12.87 14.22
15.64 17.06 Acrylate Ester Thiodiethylene bis (3,5-di- 0.5 0.5 0.5
0.5 0.5 0.5 0.5 0.5 tert-butyl-4-Hydroxy) Hydrocinnamate
2-Hydroxy-2-Methyl-1- 3 3 3 3 3 3 3 3 Phenyl-1-Propanone Bis
(2,6-Dimethoxybenzyl) (2,4,4-Trimethylpentyl) Phosphine Oxide
gamma-Mercaptopropyl 1 1 1 1 1 1 1 1 Trimethoxy Silane Test Results
Viscosity mPa .multidot. s (25.degree. C.) 430 730 1200 2000 3270
5070 8500 14,500 Urethane Concentration 1.25 1.5 1.75 2 2.25 2.5
2.75 3 (%) Fiber Pull-Out Friction 20.5 22.7 23.9 28.7 26.4 35.2
31.8 40.1 (g/mm) Crack Propagation (mm) 2.31 2.32 1.96 1.89 1.8
1.77 1.75 1.51 The oligomers in Table 17 were formulated from the
following components: H = Hydroxyethylacrylate I =
Isophoronediisocyanate PTGL 2000 =
polymethyltetrahydrofurfuryl/polytetrahydrofurfuryl copolymer diol
having an average molecular weight of 2000, (Mitsui, NY)
[0538] FIG. 9 illustrates a graph of the experimental results of
Examples 10-15 through 10-22. As can be seen from FIG. 9, as the
urethane concentration decreases the fiber pull-out friction
decreases.
EXAMPLES 10-22A THROUGH 10-24
[0539] Inner primary compositions were made by combining the
components shown in Table 18, in the same manner as described
herein above. The viscosity of the compositions was measured as
described above, and the results are shown in Table 18. The inner
primary compositions were cured by exposure to UV radiation and the
fiber friction and crack propagation properties were measured, in
the same manner as described herein above. The test results are
shown in Table 18.
18TABLE 18 Component (% by weight based on total Example Example
Example weight of composition) 10-22A 10-23 10-24 Oligomer
H-I-PTGL4200-I-H 0 49.38 45.01 Oligomer H-(I-PTGL2000).sub.2-I-H
49.38 0 0 Monomer H-HI 0 0 8.85 Ethoxylated Nonylphenol Acrylate
Ester 40.32 40.32 36.75 Thiodiethylene bis(3,5-di-tert-butyl- 0.3
0.3 0.27 4-Hydroxy) Hydrocinnamate Lauryl Acrylate 6 6 5.47
2-Hydroxy-2-Methyl-1-Phenyl-1- 3 3 2.73 Propanone Bis
(2,6-Dimethoxybenzyl) (2,4,4-Trimethylpentyl) Phosphine Oxide
gamma-Mercaptopropyl Trimethoxy Silane 1 1 .91 Test Results
Viscosity mPa .multidot. s (25.degree. C.) 9260 7050 5100 Urethane
Concentration (%) 2.61 1.72 2.61 Fiber Pull-Out Friction (g/mm)
20.85 16.85 17.4 Crack Propagation (mm) 1.62 2.06 1.74 The
oligomers and monomers in TABLE 18 were formulated from the
following components: H = Hydroxyethylacrylate I =
Isophoronediisocyanate HI = Hexane isocyanate PTGL 4200 =
polymethyltetrahydrofurfuryl/polyte- trahydrofurfuryl copolymer
diol having an average molecular weight of 4200, (Mitsui, NY) PTGL
2000 = polymethyltetrahydrofurfuryl/polyt- etrahydrofurfuryl
copolymer diol having an average molecular weight of 2000, (Mitsui,
NY)
[0540] By comparing Example 10-22A with 10-24, it becomes clear
that by using a higher molecular weight polymeric block, 4200
g/mole in Example 10-24 compared to 2000 g/mole in Example 10-22A,
the fiber friction can be significantly decreased and the crack
propagation can be increased. The urethane concentration was the
same for both Examples 10-22A and 10-24. The oligomer used
contained a polyether backbone.
EXAMPLES 10-25 THROUGH 10-28
[0541] Inner primary compositions were made by combining the
components shown in Table 19, in the same manner as described
herein above. The viscosity of the compositions was measured as
described above, and the results are shown in Table 19. The inner
primary compositions were cured by exposure to UV radiation and the
fiber friction and crack propagation properties were measured, in
the same manner as described herein above. The test results are
shown in Table 19.
19TABLE 19 Component (% by weight based on total weight of
composition) Ex. 10-25 Ex. 10-26 Ex. 10-27 Ex. 10-28 Oligomer
H-I-(NissoPB2000).sub.2-I-H 50 45 40 35 Ethoxylated Nonylphenol
Acrylate Ester 29.5 34.5 39.5 44.5 Isobornyl Acrylate 10 10 10 10
Thiodiethylene bis(3,5-di-tert-butyl-4- 0.5 0.5 0.5 0.5 Hydroxy)
Hydrocinnamate Lauryl Acrylate 6 6 6 6
2-Hydroxy-2-Methyl-1-Phenyl-1-Propano- ne 3 3 3 3
Bis(2,6-Dimethoxybenzyl) (2,4,4- Trimethylpentyl) Phosphine Oxide
gamma-Mercaptopropyl Trimethoxy Silane 1 1 1 1 Test Results
Viscosity mPa .multidot. s (25.degree. C.) Urethane Concentration
(%) 2.64 2.37 2.11 1.84 Fiber Pull-Out Friction (g/mm) 13.88 13.49
9.24 6.24 Crack Propagation (mm) 1.79 1.52 * * The oligomers and
monomers in TABLE 19 were formulated from the following components:
H = Hydroxyethylacrylate I = Isophoronediisocyanate NissoPB 2000 =
Polybutadiene copolymer diol having an average molecular weight of
2000. (Nippon Soda) * The crack propagation could not be measured
for these two coatings.
[0542] FIG. 10 illustrates a graph of the experimental results of
Examples 10-25 through 10-28. As can be seen from FIG. 10, as the
urethane concentration decreases the fiber pull-out friction
decreases. The oligomer used contained a polyolefin backbone.
EXAMPLES 10-29 THROUGH 10-32
[0543] Inner primary compositions were made by combining the
components shown in Table 20 in the same manner as described herein
above. The viscosity of the compositions was measured as described
above, and the results are shown in Table 20. The inner primary
compositions were cured by exposure to UV radiation and the fiber
friction and crack propagation properties were measured, in the
same manner as described herein above. The test results are shown
in Table 20.
20TABLE 20 Component (% by weight based on total weight of
composition) Ex. 10-29 Ex. 10-30 Ex. 10-31 Ex. 10-32 Oligomer
H-I-PTGL2000-I-H 40 40 40 40 H-BI 0 4.24 9.18 14.12 Ethoxylated
Nonylphenol Acrylate Ester 10 10 10 10 Phenoxyethyl Acrylate 45.5
41.26 36.32 31.38 Thiodiethylene bis(3,5-di-tert-butyl- 0.5 0.5 0.5
0.5 4-Hydroxy) Hydrocinnamate 2-Hydroxy-2-Methyl-1-Phenyl-1- 3 3 3
3 Propanone Bis(2,6-Dimethoxybenzyl) (2,4,4-Trimethylpentyl)
Phosphine Oxide gamma-Mercaptopropyl Trimethoxy Silane 1 1 1 1 Test
Results Viscosity mPa .multidot. s (25.degree. C.) 770 810 870 950
Urethane Concentration (%) 2.5 3 3.5 4 Fiber Pull-Out Friction
(g/mm) 39.1 40.4 42.7 47.9 Crack Propagation (mm) 1.27 1.24 1.28
1.13 The oligomers and monomers in TABLE 20 were formulated from
the following components: H = Hydroxyethyl Acrylate I = Isophorone
Diisocyanate BI = Butyl Isocyanate
[0544] FIG. 11 illustrates a graph of the experimental results of
Examples 10-29 through 10-32. As can be seen from FIG. 11, as the
urethane concentration decreases the fiber pull-out friction
decreases.
EXAMPLES 10-33 THROUGH 10-36
[0545] Inner primary compositions were made by combining the
components shown in Table 21, in the same manner as described
herein above. The viscosity of the compositions was measured as
described above, and the results are shown in Table 21. The inner
primary compositions were cured by exposure to UV radiation and the
fiber friction and crack propagation properties were measured, in
the same manner as described herein above. The test results are
shown in Table 21.
21TABLE 21 Component (% by weight based on total weight Ex. Ex. Ex.
Ex. Comp Ex. of composition) 10-33 10-34 10-35 10-36 J-1 Oligomer
H-(I-PPG2025)-I- 50 45 40 35 0 Perm2000-I-H Oligomer
H-I-(PPG2025).sub.1.4- 0 0 0 0 70 I-(Perm1000).sub.1.06-I-H
Ethoxylated Nonylphenol 10 10 10 10 25.5 Acrylate Ester Lauryl
Acrylate 6 6 6 6 0 Thiodiethylene bis (3,5-di- 0.5 0.5 0.5 0.5 0.5
tert-butyl-4-Hydroxy) Hydrocinnamate 2-Hydroxy-2-Methyl-1- 1.5 1.5
1.5 1.5 3 Phenyl-1-Propanone Bis (2,6-Dimethoxybenzyl)
(2,4,4-Trimethylpentyl) Phosphine Oxide gamma-Mercaptopropyl 1 1 1
1 1 Trimethoxy Silane Test Results Viscosity mPa .multidot. s
(25.degree. C.) 6000 Urethane Concentration 2.03 1.83 1.62 1.42 4.9
(%) Fiber Pull-Out Friction 11.87 11.5 9.9 9.8 44 (g/mm) Crack
Propagation (mm) 0 3.3 3.2 3.1 1 The oligomers and monomers in
Table 21 were formulated from the following components: H =
Hydroxyethyl Acrylate I = Isophorone Diisocyanate Perm 1000 =
Permanol KM10-1733 polycarbonate/polyether copolymer diol having an
average molecular weight of 1000 PPG2025 = PC1122 a
polycarbonate/polyether copolymer diol having an average molecular
weight of 2000
[0546] The test results in Table 21 illustrate that as the urethane
concentration decreases the fiber pull-out friction decreases and
the crack propagation increases. The test results in Table 21 also
illustrate that as the molecular weight of the polymeric block
increases the fiber pull-out friction decreases and the crack
propagation increases. The polymeric block used was a
polycarbonate.
[0547] Ribbon Assemblies
[0548] Ribbon assemblies are now well known in the art and one
skilled in the art will readily be able to use the disclosure
provided herein to prepare the novel ribbon assemblies having
enhanced ribbon strippability for the desired applications. The
novel ribbon assembly made according to this invention can be
advantageously used in various telecommunication systems. Such
telecommunication systems typically include ribbon assemblies
containing optical glass fibers, in combination with transmitters,
receivers, and switches. The ribbon assemblies containing the
coated optical glass fibers are the fundamental connecting units of
telecommunication systems. The ribbon assembly can be buried under
ground or water for long'distance connections, such as between
cities. The ribbon assembly can also be used to connect directly to
residential homes.
[0549] The novel ribbon assembly made according to this invention
can also be used in cable television systems. Such cable television
systems typically include ribbon assemblies containing optical
glass fibers, transmitters, receivers, and switches. The ribbon
assemblies containing the coated optical glass fibers are the
fundamental connecting units of such cable television systems. The
ribbon assembly can be buried under ground or water for long
distance connections, such as between cities. The ribbon assembly
can also be used to connect directly to residential homes.
[0550] The novel ribbon assemblies can also be used in a wide
variety of technologies, including but not limited to, various
security systems, data transmission lines, high density television,
and computer appliance systems. It will be appreciated that as a
result of the fundamental discoveries described herein including
the relationship between the fiber friction forces and the cohesive
strength of the coatings themselves, and the means to control and
establish such features and functions, the optical fiber art is now
able to realize significant advantages. These are primarily
exhibited, as explained above, in the stripping and cable splicing
function, but those operations are nonetheless critical in the
establishment of a ribbon/cable network of communication.
[0551] While the invention has been described in detail and with
reference to specific embodiments thereof, it will be apparent to
those of ordinary skill in the art that various changes and
modifications can be made to the claimed invention without
departing from the spirit and scope thereof. For instance, while
this invention has principally been described with reference to
ribbon constructions and assemblies of optical fibers, it is
equally adaptable to other geometric and structural arrays of
multiple fiber conduits and cables.
[0552] Accordingly, applicants believe that the scope of this
invention is defined solely by the terminology set forth in the
following claims and is not otherwise limited.
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